High School Chemistry Blog

Ionic Bonding

2011-06-20T23:54:00.000-07:00

The first explanation of chemical bonding was suggested by the properties of salts. Salts are generally crystalline solids that melt at high temperature. Sodium chloride for example, the white crystalline melt at 801^oC. The liquid after melting (molten) salt conduct an electric current. And a salt dissolved in water gives a solution that also conducts and electric current. The electric conductivity of the molten salt and the salt solution is resulted from the motion of ions in the liquid. A salt is formed between two atoms hold by ionic bonding. An ionic bonding corresponds to electrostatic attraction between positive and negative ions. It form between two atoms when one or more electrons are transferred from the valence shell of one atom to the valence shell of the other. The atom that loses electrons becomes positive ion (cation) and the atom that gains electrons becomes negative ion (anion). Any given ion tend to attract as many neighboring ions of opposite charge as possible. When the large number of ion gather together, they form an ionic solid. The losing and gaining electron of the atom cause the electron configuration changing.

The trend of electron configuration changing

The unstable elements tend to reach similar electron configuration with nearly noble gas by electron configuration changing. There are two trends, first the element atom trend to remove valence electrons , and secondly the element atom trend to gain valence electrons.

If the atom of an element removes it’s valence electron the positive charge particle occurs due to differences or proton and electron number in it. The number of electron will decrease and less then the number or proton, so that he atom change to the positive charge particle. We say the elements is electropositive elements.

In the opposite trends, if an atom gains valence electron, the number of electron increase and more than the number of proton, so that the atom change to the negative charge particle. The elements with trends to gain electron is named electronegative elements.

Example 1.1 :

Lithium has atomic number 3. It has electron configuration 2 1. It’s valence electron is 1 so lithium is unstable. To reach stability it must change to duplet system like helium by remove a valence electron and form lithium ion .

Li : 2 1 remove 1 valence electron to be Li ion (Li⁺) : 2

The lithium ion more stable than lithium atom

Example 1.2:

Magnesium has atomic number 12. The electron configuration is 2 8 1. It’s valence electron is 2 so it must change to octet system like neon with 2 8 electron configuration. Magnesium atom must remove two valence electron and form magnesium ion with (2+) number of charge.

Mg : 2 8 2 remove 2 valence electron to be Mg ion (Mg²⁺) : 2 8

Examples 1.3 :

Fluorine atom has atomic number 9. It’s electron configuration is 2 7. It need an electron to reach octet system. If fluorine atom gain an electron will form fluoride ion (F^-) that has 2 8 electron configuration like neon. So that fluoride ion more stable than fluorine atom.

F : 2 7 gain 1 valence electron to be fluoride ion (F^-) : 2 8

The ionic compound that formed between lithium and fluorine is LiF. Lithium loses an electron and fluorine gains it. The Li⁺ and F^- are formed and the attract to form neutral LiF compound. But if the compound is formed between magnesium and fluorine, the magnesium will removes two electrons, so in this case the two fluorine atoms are needed to gain two electrons. The formula of compound formed is MgF₂.

The Stability of Elements

2011-06-20T23:48:00.000-07:00

Let we see the atomic structure of noble gases. They are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn). Their atomic number are respectively 2, 10, 18, 36, 54 and 86, so that the electron configuration of noble gas atomic are :

He : 2

Ne : 2 8

Ar : 2 8 8

Kr : 2 8 18 8

Xe : 2 8 18 18 8

Rn : 2 8 18 32 18 8

Except helium the noble gas has eight valence electrons that form four electron pairs to result stability. The system of electron configuration with eight valence electron named octet rule. Helium only has two valence electrons, so that it form an electron pair only. This system named duplet rule. If the atoms of an element has octet or duplet system of it electron configuration, this element has high stability like noble gases. For this reason the unstable elements tend to reach duplet or octet system by electron configuration changing.

Flame Colour of Group IA (Group 1)

2011-06-20T23:38:00.000-07:00

Flame colors are produced from the movement of the electrons in the metal ions present in the compounds.
For example, a sodium ion in an unexcited state has the structure 1s2 2s2 2p6. When you heat it, the electrons gain energy and can jump into any of the empty orbitals at higher levels - for example, into the 7s or 6p or 4d or whatever, depending on how much energy a particular electron happens to absorb from the flame.
Because the electrons are now at a higher and more energetically unstable level, they tend to fall back down to where they were before - but not necessarily all in one go.
An electron which had been excited from the 2p level to an orbital in the 7 level, for example, might jump back to the 2p level in one go. That would release a certain amount of energy which would be seen as light of a particular color.
However, it might jump back in two (or more) stages. For example, first to the 5 level and then back to the 2 level.
Each of these jumps involves a specific amount of energy being released as light energy, and each corresponds to a particular color.
As a result of all these jumps, a spectrum of colored lines will be produced. The color you see will be a combination of all these individual colors.
The exact sizes of the possible jumps in energy terms vary from one metal ion to another. That means that each different ion will have a different pattern of spectral lines, and so a different flame color.

The colors
The colors in the table are just a guide. Almost everybody sees and describes colors differently. I have, for example, used the word "red" several times to describe colors which can be quite different from each other. Other people use words like "carmine" or "crimson" or "scarlet", but not everyone knows the differences between these words - particularly if their
Li red
Na strong persistent orange
K lilac (pink)
Rb red (reddish-violet)
Cs blue? violet? (see below)

What do you do if you have a red flame colour for an unknown compound and don't know which of the various reds it is?
Get samples of known lithium, strontium (etc) compounds and repeat the flame test, comparing the colours produced by one of the known compounds and the unknown compound side by side until you have a good match.
________________________________________
Note: I don't have confidence in the caesium flame colour. There is total disagreement about this on the web and in the books I have looked at, and I have never seen this flame colour myself. However, I have received a helpful email from a student who says: "At my school we did some flame testing experiments, and . . . caesium is actually either blue or violet, depending on the way you look at it. I think it looks more violet than blue, but it sort of changes each time you do it." (Kara Gates, March 2006). If you thought chemistry was clear-cut, you are sadly mistaken!
________________________________________

CHARACTERISTICS OF LIVING ORGANISMS

2011-04-25T22:57:00.000-07:00

Biology is the study of living things. But, life is very difficult to define.For example, we often find difficulty to ensure if the virus is a living thing or a non-living thing. We must know some characteristics of the object to determine it is included in the group of living thing or non-living thing. Every living thing has the characteristics of living things. What are the characteristics of living things? After you knowing the characteristics of living things, you will find the variety of living organisms. The vary not only physically, but also structurally.
We must know the characteristics of living things to classify something is living thing or non-living thing. The characteristics of living things are as follow.

1. Movement
Movement is the change of position, either the hole or a part of the body. Every living organism can move freely or change its position. Human and animals need additional devices to move called movement devices. Movement devices can be the feet to run, fins to swim, wings to fly etc. See picture 2.1.1. On the other hand, movement of the plants only involve some part of their bodies, so that they look like unmoved. The end of the stalk moves to light arrival, roots go down deep into the soil and mimosa pudica‘s leaves shrink when they are touched.

2. Sensitivity
Sensitivity is the ability of living things to respond of stimulation. It means that every living thing react to everything changing around them. This reaction appear when the stimulation coming from the surruondings. Stimulation can be in the form of light, heat, coldness, smell, cold, gravitation, sense etc. Humans and animals using senses to identify the stimuli. For examples, eyes are sensitive to light, ears are sensitive to sound and nose is sensitive to smell thing. Palnts don’t has sense as humans and animals, but sensitive with stimuli. For examples, the end of branch always moves toward the coming light, the end of root is sensitive to gravitation force and the leaves of mimosa pudica shrink when they are touched.

3. Nutrition
Living things need food and water. Food is useful for retaining their survival, gaining some energies and growths. Whereas water plays a role as a solvent in the body. Every living thing has some different ways to gain food. Greeneries can produce their food by themselves by changing organic substances (water and carbondioxide) into organic substances (glucose) with the help of sunlight. The process is called photosynthesis. Because of their ability to produce their food by themselves, the plants are called autotrof. Animals and plants depends on other living organism, so that they are heterotrof.

4. Respiration
Respiration is the taking over of oxygen from surroundings and releasing of carbondioxide from the body. Oxygen is used to change nutrition into energy chemically. Gained energy is used to some kinds of body activities. Humans and animals which living on the land take a breathe using lungs. Water animals generally take a breath using gill and worms take a breath using skins. Plants breathe to take oxygen through stomata’s leaves and lentisel’s stalk.

5. Growth
Growth is the reversible increasing of volume and size of living things. This increasing happen because of the increasing of cell amount and size. Every living thing grow from small size to big size. Babies which are smaller when they were born will grow bigger. Seeds which are implanted will grow become seedling and then growth into bigger plant.

6. Adaptation
Adaptation is the ability of living things to adapt tyo their surroundings. There are three kinds of adaptation, i.e:
a. Morphological adaptation is the adaptation of their devices. For its examples, eagle has sharp claws to leap on its victim. Water lily has wide leaves to extend vaporized area.
b. Physiological adaptation is the adaption of living things to their surroundings using the function of body’s devices. For example, camel’s dirt is dry, but its urine is viscous.
c. Habitual adaptation is the adaptation of living things to their surroundings by showing certain attitude. For example, chameleon changes its skin’s colour.

7. Reproduction
Reproduction is the ability of living things to multiply for surviving their existence. There are two kinds of reproduction ways, i.e:
a. Generative reproduction is the reproduction which involves sperms and ovum.
b. Vegetative reproduction is the reproduction which doesn’t involve sperms and ovum.
There are natural and artificial vegetation.

8. Regulation
Regulation is the process of arraging appropriateness in the body of organisms which is controlled by nerves and hormones.

9. Excretion
Excretion is the process of releasing residues from body metabolism. Food oxidation process doesn’t only result in energy but also produce residues which must be released from the body. When the residues are not released from the body, they will be hazardous for the body.

Ionization Energy

2009-09-07T05:18:00.000-07:00

Ionization energy is the energy required by an atom in the form of gas to remove one electron to form positive ions.

The lower the ionization energy, the easier an electron released an atom to form negative ions.
In the periodic table, ionization energy values showed periodicity. In a period from left to right, the ionization energy increased. In one class, from left to right, ionization energy decreased.

Electron Affinity

2009-09-04T05:26:00.000-07:00

Electron affinity is the energy released by an atom (in the form of gas) when an electron capture to form negative ions. Since the energy is released, given the price of the electron affinity of the minus sign.
The greater the energy released, the negative ions are formed more stable. IIA group elements and VIIIA not form a stable negative ions. Prices positive electron affinity.
In one period, from left to right, electron affinity values tend to increase. In one class, from top to bottom, the electron affinity values tend to decrease.

Introduction of Chemical Bonds

2009-06-10T10:20:00.000-07:00

An atom consists of the atomic core and the atom's skins. Atomic core consists of proton particles that is positive particles and neutrons that ia neutral particles. Meanwhile, electron skins contains electron that is negative particles. The place where electrons found is called the orbital. Electrons first put themselves on the orbitals which has the lowest energy level.

Two or more atoms can form a chemical bond using the valence electrons in order to form a molecule. If the atoms does not have a strong difference electronegativity (or little difference of electronegativity), valences electron of atoms are used together formed a covalent bond. If the atoms has a large difference of electronegativity, the atoms are formed ion bonds.

The atoms bonded to obtain stable configuration that is formed as electrons configuration of noble gas elements.

In the covalent bond, electrons used together by the atoms so that the atoms has electron configuration such as electron configuration noble gas elements. For example, hydrogen has 1 valence electron and oxygen has 6 valence electrons. Both types of elements are formed of water molecules (H₂O).
If a bond has a pair of electrons used to bond, called single covalent bond. There are also covalent bong type with two pairs of electrons, called double covalent bond. If the covalent bond using three electron pairs, called the triple cobalent bond. In some cases, the electron pair shared come from only one atom of it, called coordination covalent bond or coordinates covalent bond or covalent dativ bond or semipolar covalent bond.

At the ion bond, the atoms has a high value of electronegativity capture elctrons form a negative ion, while the atoms that has a low value of electronegaivity release the valense electrons formed positive ion. With the capture or release electrons, the atoms become stable formed electron configuration like elements configuration of noble gas. Although the atoms in the compound does not use the pair electron together, but the atoms have a strong bond each other because the atoms cargo is different. In an ion compound, all the ions form a crystal lattice structure.

Calculating the Change of Enthalphy Using Calorimeter

2009-04-25T19:55:00.000-07:00

When the changes of enthalpy or heat involved in the chemical reactions can be determined using a mathematical calculation, the amount of the heat in a chemical reaction can be measured using an experiment in the laboratory. Measurement heat reaction can be carried out using a tool called a calorimeter.

Calorimeter is an instrument used to measure the amount of heat given or taken in a particular process. A simple thermometer consists of a vessel isolation, mixer equipment, and thermometers.
Generally, the calorimeter wrapped by heat insulator material, such as polystyrene or styrofoam. The material can be used to reduce heat exchange between the system and environment, so that the pressure in the calorimeter is relatively fixed. It is because the measurement of heat using calorimeter should be done on the constant pressure. How do I measure heat using calorimeter? To understand how to measure heat using calorimeter, pay attention to the following explanation .
To measure heat using calorimeter, a heat source stored in the calorimeter and the water is stirred until equilibrium is reached, then the increase of temperature noted by reading the thermometer. In this case, the number of heat were released by the system in the calorimeter can be calculated.
The pressure in the calorimeter is relatively fixed, then the change in heat of system is equal with the enthalpy changes. This is expressed with the following equation.
ΔH = Q
Because the calorimeter vessel wrapped using the insulator material, they have not considered the heat absorbed and released by the system to and from the environment, so that heat of system is equal to zero.

Q_reaction + Q_calorimeter + Q_solution = Q_system
Q_reaction + Q_calorimeter + Q_solution = 0
Q_reaction = - (Q_calorimeter + Q_solution)

The heat of calorimeter is influenced by the heat capacity (C). If the heat capacity is relatively small (the heat pf calorimeter can be ignored), then the above equation can be written as follows.

Q_reaction =-Q_solution
Q_solution = m c ΔT

with:
Q = heat (Joule)
m = solution mass (g)
c = the specific heat of solution (J/g^oC)
ΔT = T_final - T_initial = the change in temperature (^o or K)
Note:
Specific heat is the amount needed to raise the temperature of one gram of substance by one degree Celcius at a constant pressure.
The calculation above is used if the heat capacity of calorimeter is ignored, but if the quantity is considered, the heat fo the calorimeter must be involved in the calculated. In this case, the amount of the heat calorimeter can be determined using the following equation.

Q_calorimeter = C_k ΔT

With:
C_k = capacity of calorimeter (J/g^oC)

So
Q_reaction = - (Q_calorimeter + Q_solution)

In fact, the number of heat absorbed by calorimeter is relatively small than the heat absorbed ny the solution, so that in some types of calorimeter, the price of C_kΔT can be ignored.

The heat measurement using a calorimeter as discussed above are generally made for the reactions involving the system in the form of solution .However, for chemical reactions involving a combustion or reaction to determine the amount of energy contained in food the more accurate calorimeter is used, that is bomb calorimeter.
Basically, a bomb calorimeter consisting of a chamber where the substance is burned, the water filled into the chamber, a stirrer, a thermometer, and the contact wire.
The combustion reactions that occur inside the bomb will produced heat absorbed by the water and the bomb at the same temperature, so that the water temperature increases. Because there is no heat transfer between systems and environment during the reaction, then:
Q_reaction = - (Q_calorimeter + Q_water)
= - (ΔT C_bomb + m C_water ΔT)
where:
C_bomb = heat capacity of the bomb calorimeter (J/g^oC)

Measuring pH Solution Using Acid Base Indicator

2009-04-10T00:31:00.000-07:00

Measurement Tool	pH range	Acid	Base
Litmus Phenolphtalein Metil orange Metil red Bromtimol blue Universal indicator pH meter	5.5 - 8 8.3 - 10 2.8 - 4 4.2 - 6.3 6.0 - 7.6 0 - 14 0 - 14	Red No color Red Red Yellow -- --	Blue Red Yellow Yellow Blue -- --

Example: Next stretch indicator data basa acid.

Indicator	Stretch pH	Changes color
Metil purple Bromkesol green Bromtimol blue	0.5 - 1.5 3.8 - 5.4 6.0 - 7.6	Yellow - purple Yellow - blue Yellow - blue

Determining with the value of pH with indicator solution data

given:
with metil purple indicator, purple
with bromkesol green indicator, blue
with bromtimol blue indicator, yellow
Determine the pH range of the solution!
Answer:
According to data range pH indicator:
With metil purple indicator, purple, the pH solution > 1.5.
With bromkesol green indicator, blue, the pH solution > 5.4.
With bromtimol blue indicator, yellow, the pH solution <>

Metal and Non-metallic Elements

2009-04-02T17:35:00.000-07:00

Nowadays, more than 100 elements have been found. Elements have certain properties that distinguish between the one elements with the other elements. We can distinguish the elements to the metal elements, metaloid elements and non-metallic elements.

Some of the properties of the metal:
Malleability: the metal can be formed without cracks.
Ductility: the metal can be drawn without a change in the surface.
Toughness: metal can be crooked.
Hardness: resistance to the penetration of metal or other hard objects puncture.

Commonly non-metal elements in gas phase at room temperature. While metaloid elements have the properties between metal elements and non-metallic elements.

In the table of periodic system of the elements, non-metallic elements located on the left side (except hydrogen) and non-metallic elements is located on the right side. Metal and non-metallic elements is separated by the metaloid elements which is located in the middle table of periodic system of the elements.

Metaloid elements are Boron (B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te) Polonium (Po), Astatine (At). Some of the metal elements are Sodium (Na), Iron (Fe), Coppre (Cu) etc. Some of the non-metallic elements are hydrogen (H), Helium(He), Oxygen (O), Nitrogen (N) etc.

Stoichiometry: pH of Strong Acids and Strong Bases

2009-04-02T16:13:00.000-07:00

The strength of an acid or a base is determined by the value of equilibrium acid constant (Ka). The greater Ka, the stronger acidity. Conversely, a strength of a base determined by the the value of equilibrium base constant (Kb). The greater Kb, the greater properties of the base.

Strength acid and strength base closely related to the ability of the acid or base ionized in the water. Strong acid and strong base fully ionized in the water, while the weak acid and weak base partial ionized in the water. The amount of ionized mole on the weak acid or base is vary depending on the size of the degree of ionization rates (α).

Acids that includes a strong acid is HCl, HBr, HI, H₂SO₄, HNO₃, HClO₄. In addition, other acids can be considered as a weak acid. That acids is mono valence except H2SO4 bivalen according to the number of its H⁺. Its H⁺ concentration can be calculated using the formula:

[H⁺] = M x val
where:
[H⁺] = concentration of H⁺
M = concentration of acid
val = acid valency
Its acid pH can be calculated using the formula:
pH = - log [H₊]

Example: Calculate pH 0.2 M HCl
[H⁺] = M.val = 0.2 M x 0.2 M = 1 = 2x10^-1 M
pH = - log [H⁺] = - log 2x10^-1 = 1 - log 2

While for base, bases which is considered as strong bases is NaOH, KOH, Ca(OH)₂, Sr(OH)₂ and Ba(OH)₂. Other bases can be considered as weak bases. NaOH and KOH is mono valence base. Ca(OH)₂, Sr(OH)₂ and Ba(OH)₂ is bivalen bases according to the number of its OH^-. Concentration of OH can be calculated using the formula:

[OH^-] = M x val
where:
[OH^-] = concentration of OH^-
M = concentration of base
val = base valency
base its pH can be calculated using the formula:
pOH = - log [OH^-]
pH = 14 - pOH

Example: Calculate pH Ba(OH)₂ 0.05 M
[OH^-] = M M.val = 0.05 x 2 = 0.1 M = 1x10^-1 M
pH = - log [OH^-] = - log 1x10^-1 = 1

Acid Base Neutralization Reaction

2009-03-31T22:22:00.000-07:00

1. Base + acid → salt + water
Example: HCl + KOH → KCl + H₂O
2. Base oxide + acid → salt + water
Example: 2NaOH + CO₂ → Na₂CO₃+ H₂O
3. Base oxide + acid → salt + water
Example: CaO + 2HCl → CaCl₂ + H₂
4. Acid oxide + base oxide → salt base
Example: SO₃ + CaO → CaSO₄
5. Metal + acid → salt + H₂ gas
Example: Fe + H₂SO₄ → FeSO₄ + H₂
6. Metal1 + salt1 → salt2 + metal2
Example: FeSO₄ + Ca → Fe + CaSO₄Terms: Salting at fifth number, the metal must be on the left H + in the array Volta. Salting at sixth number, metal1 must be located on the left in metal2 array Volta.
Volta array:
Li - K - Ba - Ca - Na - Mg - Al - Mn - Zn - Cr - Fe - Co - Ni - Sn - Pb - (H) - Sb - Bi - Cu - Hg - Ag - Au - Co

Links Exchange

2009-03-31T22:08:00.000-07:00

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If you want to exchange links, please write in comments. I would like to put your link when you put my link at your blog. My blog titled High School Chemistry Blog with address http://gundulshare.blogspot.com. You may have to write your blog description also.

About Me

2009-03-31T21:48:00.000-07:00

I'm just a man who are still learning. Now, I'm busy teaching chemistry at a school in Semarang, Central Java, Indonesia.
Email: panserbiru@gmail.com
Yahoo ID: arhie_hend@yahoo.com

Site Map

2009-03-31T21:07:00.000-07:00

Basic Chemistry
Measuring pH Solution Using Acid Base Indicator
Water Equlibrium Constant and Acid Base Strength
Acid Base Theory
Material Classification
Physics and Chemist Changes
About Atoms and Elements
Hydrogen
About Chemical Science
Atomic Number and Mass Number of Atom
Isotope, Isobar and Isoton
PPM (Part Per Million)
Oxidation Number
History of Atom Models

Anorganic Chemistry
Metal and Non-metallic Elements

Physic Chemistry
Calculating the Change of Enthalphy Using Calorimeter

Analytic Chemistry
Acids Bases Neutralization Reaction
Stoichiometry: pH of Strong Acids and Strong Bases

Organic Chemistry

Biochemistry

Other
Leave The Cigarettes
About Google Search
First Posting in 2009
Indonesia Win
Nanotechnology: Really Just Happen in My Dreams

For Indonesian Only
Unsur Golongan Utama
Kinetika Reaksi
Kelarutan sebagai Fungsi Suhu
Membuat CD Media Pembelajaran Interaktif Menggunakan Flash
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Study Tour Part 1: Going to Ketep
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Water Equilibrium Constant and Acid Base Strength

2009-03-27T22:40:00.000-07:00

Water Equilibrium Constant
Water is a very weak electrolyte. Ionization occurs in water:
H₂O → H⁺ + OH^-

K_[H₂O] = [H⁺] [OH^-]
Kw = [H⁺] [OH^-]
At a temperature of 25ºC, Kw = 1.10^-14, so that [H⁺] = [OH^-] = 1.10^-7.
Acid solution [H⁺]> 1.10^-7.
Base solution [OH-] < 1.10^-7.

Acid Base Strength
Acid base strength expressed in H⁺ or OH^- concentration. Acid with the high concentration of H⁺ has greater acid strength than with the acid H⁺ with low concentration. Similarly base with its concentration of OH^-.
Example:
HCl → ....H⁺ ....+ ...Cl^-
0.1 M .. 0.1 M 0....0.1 M
H₂SO₄ → ....2H⁺ ...+ ..SO₄^2-
0.1 M .....0.2 M...... 0.1 M
At the same concentration (0.1 M), H₂SO₄ is more acid than HCl because the H₂SO₄ has greater H⁺ concentration than HCl.

Acid Base Theory

2009-03-27T21:40:00.000-07:00

1. Arrhenius Theory
Acid: electrolyte substance which in water produce H⁺ ion.
Example: HBr_(aq) → H⁺_(aq) + Br^-_(aq).
Base: electrolyte substance which in water produces OH-.
Example: KOH_(aq) → K⁺_(aq) + OH^-_(aq).

2. Bronsted Lowry Theory
Acid: substance that gives proton or H^+.
Base: oxygen proton or accept a H⁺.
Example: H₂O + NH₃ → NH₄⁺ + OH^-
acid1 basa1 acid2 base2
Base acid conjugation couple has characteristics deviate only 1 H⁺.
For the reaction on the spouse: H₂O and OH^-, NH₃ and NH₄⁺.
Substance amphipirotic/amfoter: substances that can give or receive
the proton (H⁺). Ex: H₂O, H₂PO₄^-,HPO₄^2-.

3. Lewis Theory

Acid: electron pair acceptor.
Base: electron pair donor.
Example: BF₃ + :NH₃ → H₃N:BF₃
NH₃ to give a pair of electrons to BF₃, NH₃ as base and BF₃ as acid.

Praktikum Kinetika Reaksi

2009-03-26T20:17:00.000-07:00

Untuk download PDFnya klik disini.

I. TUJUAN

Mempelajari kinetika reaksi dari hidrogen peroksida dengan asam iodida.

II. LATAR BELAKANG

Reaksi hidrogen peroksida dengan kalium iodida dalam suasana asam (dan dengan adanya natrium tiosulfat) akan membebaskan iodida yang berasal dari kalium iodida. Kecepatan reaksi ini sangat tergantung kepada peroksida, kalium, iodida dan asamnya.

Bila reaksi ini merupakan reaksi irreversibel (karena adanya natrium tiosulfat) yang akan berubah iodium bebas menjadi asam iodida kembali, kecepatan reaksi yang terjadi besarnya seperti pada pembentukannya, sampai konsentrasi terakhir tak berubah.

Pada percobaan ini kecepatan reaksi hanya tergantung pada berkurangnya konsentrasi hidrogen peroksidanya saja, sehingga reaksi ini mengikuti reaksi orde 1.

Pada larutan yang mempunyai keasaman tinggi atau kadar iodida yang tinggi akan didapatkan kecepatan reaksi yang lebih besar. Untuk menghitung kecepatan reaksi yang akan dapat hitung dengan penjabaran kecepatan reaksi yang memerlukan besarnya konstanta kecepatan reaksi adalah sebagai berikut:

-d C/dt = K Cⁿ

Untuk reaksi orde 1, n = 1. hasil integrasi didapatkan:

-∫ d C/C = K dt

ln C₀^t = - Kt

ln C_t/C₀ = - Kt

K = -(1/t) ln (C_t/C₀) atau K = (1/t) ln (C₀/C_t)

Dimana

C₀ = konsentrasi mula-mula

C_t = konsentrasi setelah t detik

Di dalam percobaan ini, volume tiosulfat yang dititrasi sebanyak (b) merupakan jumlah peroksida yang bereaksi selama t detik. Maka, konsentrasi peroksida setelah t detik besarnya (a-b). Jika a adalah banyaknya tio yang setara dengan peroksida pada saat t₀ atau mula-mula, persamaannya menjadi:

K = (1/t) ln (a/a-b)

ln (a-b) = Kt + ln a

Dengan membuat grafik ln (a-b) vs t, maka akan didapatkan –K sebagai angka arah dari garis lurus tersebut (gradien), sehingga arah K dapat ditentukan.

III. ALAT DAN BAHAN

Alat: buret 50 L, erlenmeyer 1 L, gelas ukur 100 mL, stopwatch, gelas piala 200 mL, labu takar 100 mL dan pengaduk magnet.

Bahan: H₂O₂ 3%, H₂SO₄ 2 M, KMnO₄ 0,1 M, KI kristal, H₂SO₄ pekat, Na₂S₂O₃0,1 M dan larutan kanji encer.

IV. CARA KERJA

1. Mencari ekivalen H₂O₂ dengan tiosulfat.

2. Isi buret dengan larutan standar tiosulfat

V. DATA PENGAMATAN

1. Titrasi H₂O₂ dengan KMnO₄

No.

Vol H₂O₂

(mL)

Vol KMnO₄ (mL)

V₁

V₂

V₃

4,2

4,1

2. Titrasi KMnO₄ dengan tiosulfat

No.

Vol KMnO₄

(mL)

Vol Na₂S₂O₃ (mL)

V₁

V₂

49,8

48,7

No.

Waktu (t)

Vol Na₂S₂O₃ (mL)

No.

Waktu (t)

Vol Na₂S₂O₃ (mL)

07:27

12:81

23:01

29:28

34:39

46:98

2,0

6,7

11,0

13,5

16,2

20,5

10.

11.

12.

13.

56:47

63:60

69:30

76:49

91:26

96:80

106:81

24,3

26,8

28,7

31,8

37,0

39,0

42.3

VI. PEMBAHASAN

Percobaan ini bertujuan untuk mempelajari kinetika reaksi dari hidrogen peroksida dan asam iodida. Iodida yang berasal dari kalium iodida akan dibebaskan dengan adanya natrium tiosulfat dalam suasana asam.

Volume tiosulfat yang dititrasi sebanyak (b) merupakan jumlah peroksida yang bereaksi selama t detik untuk menyetarakan sejumlah peroksida dan tiosulfosfat, maka perlu dicari ekivalennya terlebih dahulu. Oleh karena itu dilakukan titrasi pada peroksida dan tiosulfat menggunakan larutan standard KMnO₄. Dari hasil titrasi, setelah dihitung diperoleh perbandingan volume peroksida dan volume tisulfat adalah 1 : 2.

Untuk mengetahui konsentrasi peroksida yang bereaksi, di lakukan titrasi menggunakan natrium tiosulfosfat. Volume tiosulfat yang digunakan merupakan jumlah peroksida yang bereaksi selama t detik (b). Berkurangnya jumlah peroksida inilah yang mempengaruhi laju reaksi. Banyaknya tiosulfat yang setara dengan peroksida mula-mula (a) harus diketahui agar dapat menghitung konsentrasi peroksida setelah t detik (a-b).

No.	a-b	t	ln (a-b)
1.	0.0980	7.54	-2.322787
2.	0.0933	10.20	-2.371935
3.	0.0890	23.01	-2.419118
4.	0.0865	29.28	-2.447610
5.	0.0838	34.39	-2.479322
6.	0.0795	46.98	-2.531998
7.	0.0757	56.47	-2.580977
8.	0.0732	63.60	-2.614559
9.	0.0713	69.30	-2.640859
10.	0.0682	76.49	-2.685310
11.	0.0630	91.26	-2.764620
12.	0.0610	96.80	-2.796881
13.	0.0577	106.81	-2.852498

Dari hasil analisa data di buat grafik ln (a – b) vs t. Akan diperoleh gradiennya sebagai - K. Dari perhitungan analisa data, grafik yang terbentuk adalah sebagai berikut:

Persamaan regresinya adalah y = -0,0051x – 2,2984

ln (a-b) = - Kt + In a.

sehingga, K = 0,0051

Laju reaksi V = 0,051 C

VII. KESIMPULAN DAN SARAN

a. Kesimpulan

1. Natrium tiosulfosfat dapat membebasan iodida dari kalium iodida.

2. Kecepatan reaksi bergantung pada berkurangnya konsentrasi H₂O₂.

3. Reaksi H₂O₂ dan Kl merupakan reaksi orde I dengan persamaan regresi y = -0,0051x – 2,2984, diperoleh harga K = 0,0051 dan R² = 0.9968

b. Saran

1. Praktikan hendaknya melakukan persiapan secara matang.

2. Praktikan lebih teliti dalam melakukan pengamatam

3. Alat yang digunakan sesuai dengan standar.

VIII. DAFTAR PUSTAKA

1. Tim Dosen Kimia Fisika. 2004. Petunjuk Praktikum Kimia Fisika I. Semarang. Jurusan Kimia FMIPA UNNES.

2. Wahyuni, Sri.2003.Buku Ajar Kimia Fisika 2.Semarang:UNNES.

Semarang, 22 Oktober 2005

Praktikan

Ari Hendriayana

ANALISA DATA

Mencari ekivalen H₂O₂ dengan tiosulfat

Vol H₂O₂ : vol KMnO₄ = 10 : 4

= 25 : 10

Vol KMnO₄: Vol tio sulfat = 10 : 50

Maka Vol H₂O₂ : Vol tio sulfat = 25 : 49,25

≈ 1 : 2

Vol total tio setara dengan jumlah peroksida saat t_o

= 50 x 2 = 100 ml = 100 mL x 0,1 m = 10 mmol

[Na₂S₂O₃] mula-mula a = 0,1 M

a = 0,1 M

[H₂O₂] setelah t detik = a – b

1). t₁= 7,27 detik

b₁= 2 ml x 0,1 M = 0,2 mmol

a – b = 10 – 0,2 = 9,8

= 0,098 M

ln (a –b_i) = ln 0,098 = -2.322787

2). t₂= 12,81 detik

b₂=6,7 ml x 0,1 M = 0,67 mmol

a – b₂= 10 – 0,67 = 9,33 mmol

= 0,0933 M

ln(a – b₂) = ln 0,0933 = -2.371935.

3). t₃= 23,01 detik

b₃ = 11 ml x 0,1 M = 1,1 mmol

a – b₃ = 10 – 1,1 = 8,9 mmol

= 0,089 M

ln(a – b₃) = ln 0,089 = -2.419118

4). t₄= 29,28 detik

b₄ = 13,5 ml x 0,1 M = 1,35 mmol

a – b₄= 10 – 1,35 = 0,65 mol

= 0,0865 M

ln(a – b₄) = ln 0,0865 = -2.447610

5). t₅= 34,39 detik

b₅ = 16,2 ml x 0,1 M = 1,62 mmol

a – b₅ =10 – 1,62 = 8,38 mmol

= 0,0838 M

ln(a - b₅) = ln 0,0838 = -2.479322

6). t₆ = 46,98 detik

b₆ = 20,5 ml x 0,1 M = 2,05 mmol

a – b₆ = 10 – 2,05 = 7,95 mmol

= 0,0795 M

ln(a – b₆) = ln 0,0795 = -2.531998

7). t₇ = 56,47 detik

b₇= 24,3 ml x 0,1 M = 2,43 mmol

a – b₇ = 10 – 2,43 = 7,57 mmol

= 0,0757 M

ln(a – b₇) = ln 0,0757 = -2.580977

8). t₈ = 63,60 detik

b₈ = 26,8 ml x 0,1 M = 2,68 mmol

a – b₈ = 10 – 2,68 = 7,32 mmol

= 0,0732 M

ln(a – b₈) = ln 0,0732 = -2.614559

9). t₉ = 69,30 detik

b₉ = 28,7 ml x 0,1 M = 2,87 mmol

a – b₉ = 10 – 2,87 = 7,13 mmol

= 0,0713 M

ln(a – b₉) = ln 0,0713 = -2.640859

10). t₁₀ = 76,49 detik

b₁₀ = 31,8 ml x 0,1 M = 3,18 mmol

a – b₁₀ = 10 – 3,18 = 6,82 mmol

= 0,0682 M

ln(a – b₁₀) = ln 0,0682 = -2.685310

11). t₁₁ = 91,26 detik

b₁₁ = 37 ml x 0,1 M = 3,7 mmol

a – b₁₁ = 10 – 3,7 = 6,3 mmol

= 0,063 M

ln(a – b₁₁) = ln 0,063 = -2.764620

12). ). t₁₂ = 96,80 detik

b₁₂ = 39 ml x 0,1 M = 3,9 mmol

a – b₁₂ = 10 – 3,9 = 6,1 mmol

= 0,061 M

ln(a – b₁₂) = ln 0,061= -2.796881

13). ). t₁₃ = 106,81 detik

b₁₃ = 42,3 ml x 0,1 M = 4,23 mmol

a – b₁₃ = 10 – 4,23 = 5,77 mmol

= 0,0577 M

ln(a – b₁₃) = ln 0,0577= -2.852498

Kelarutan Sebagai Fungsi Suhu

2009-03-25T15:36:00.000-07:00

Download file PDFnya disini.

Saya masukkan pembahasannya aja sebagai preview.

Percobaan ini membahas kelarutan sebagai fungsi suhu, dimana zat yang digunakan adalah asam oksalat (H₂C₂O₄) dan sebagai larutan penitrasinya adalah larutan NaOH 0,2 N. Kelarutan di sini sangat dipengaruhi oleh suhu. Apabila suhunya dinaikkan, maka kelarutannya akan besar. Sedangkan jika suhunya diturunkan, maka kelarutannya kecil. Pada suhu 40°C, larutan asam oksalat diambil 10 ml kemudian dititrasi, ternyata volume larutan NaOH yang dibutuhkan untuk menitrasi sebanyak 13,47 ml. Sedangkan untuk suhu 30°C volume larutan NaOH yang digunakan untuk titrasi sebanyak 12,47 ml. Pada suhu 20°C dan 10°C dibututuhkan larutan NaOH masing-masing sebanyak 9,23 ml dan 5,53 ml.

Pada percobaan ini volume larutan NaOH yang digunakan untuk menitrasi semakin banyak dengan bertambahnya suhu. Oleh karena itu untuk menghemat waktu dan bahan, maka seharusnya menitrasi dengan NaOH yang molaritasnya 0,5. Pada suhu 40°C, molalitas larutan H₂C₂O₄ adalah 0,01347 m. Sedangkan pada suhu 30°C, 20°C dan 10°C molalitasnya masing-masing adalah 0,0127 m, 0,00923 m dan 0,00553 m.

Setelah dialurkan menjadi grafik log m vs 1/T, dihasilkan persamaan regresi y = -1161.1x + 1.8872 sehingga delta HDSnya sebesar 1161,1 kj/mol. Tanda minus hanya menunjukkan arah kemiringan kurva.

Hasil percobaan ini jauh dari sempurna, kemungkinannya disebabkan oleh beberapa hal antara lain:

1. Kekurangtelitian praktikan saat percobaan, dalam pembuatan larutan.

2. Validitas alat yang digunakan.

3. Pengamatan yang kurang teliti.

4. Kesalahan analisa data.

Penggolongan Materi (Material Classification)

2009-03-20T07:14:00.000-07:00

Ilmu kimia mempelajari materi. materi adalah sesuatu yang mempunyai massa dan menempati ruang. Materi dapat digolongkan ke dalam zat tunggal dan campuran.

ZAT TUNGGAL

Unsur

Unsur merupakan zat tunggal yang tidak bisa dipisahkan menjadi zat lain yang lebih sederhana. Contoh: hidrogen (H), oksigen (O), besi (Fe) dan lain-lain.

Senyawa

Senyawa adalah zat tunggal yang dapat dipisahkan menjadi zat lain yang lebih sederhana. Suatu senyawa hanya dapat dipisahkan menjadi unsur-unsur penyusunnya melalui perubahan kimia. Contoh senyawa: air (H₂O), alkohol (C₂H₅OH) dan lain-lain.

CAMPURAN

Larutan

Larutan adalah campuran homogen yang terdiri dari dua jenis zat atau lebih. Homogen artinya tidak ada bidang batas antara zat yang satu dengan yang lain (meski diamati menggunakan mikroskop ultra) atau mempunyai satu fasa. Larutan sering disebut secara spesifik sebagai larutan sejati. Ukuran partikel larutan sejati kurang dari 1.10^-9 nm. Contoh: larutan gula.

Koloid

Koloid merupakan jenis campuran yang memiliki karakteristik khusus sehingga dipelajari pada pembahasan tersendiri. Secara kasat mata koloid terlihat homogen, tetapi jika diamati menggunakan mikroskop ultra akan terlihat jelas bahwa koloid merupakan campuran heterogen. Ukuran partikel koloid antara 1.10^-9 - 1.10^-7 nm. Contoh: susu, agar-agar dan kabut.

(gambar diambil dari: http://roseskitchen.files.wordpress.com/2007/06/pandan-custard-agar-agar-slices.jpg)

Suspensi

Suspensi merupakan campuran heterogen dengan ukuran partikel lebih besar dari 1.10^-7 nm. Contoh: campuran tepung terigu dengan air.

=============================================================

Chemistry learning all about materials. The material is anything that has mass and occupies space. Materials can be classified into a single substance and mixture.

SINGLE SUBSTANCE

1. Element
Element is a single substance that can not be separated into other simple substances. Example: hydrogen (H), oxygen (O), iron (Fe) and others.

2. Compound
Compound is a single substance that can be separated into other simple substances. A compound can only be separated into elements by chemical changes. Example compound: water (H₂O), alcohol (C₂H₅OH) and others.

MIXED

1. Solution
Solution is homogeneous mixture and consists of two or more kinds of substances. It means that is no homogeneous field boundary between the substance of one another (although observed using ultra-microscope) or to have one phase. Solution is often referred to specifically as the pure solvent. The size of pure solvent particles less than 1.10^-9 nm. Example: sugar solution.

2. Colloid
Colloid is a mixture that have special characteristics so that discussed in aother part. The colloidal look homogeneous, but when colloid observed using a ultra-microscope will be visible to clear that the colloid is a heterogeneous mixture. The size of colloidal particles between 1.10^-9 - 1.10-⁷ nm. Examples: milk, jelly and fog.
(picture taken from: http://www.jaylichtman.com/pictures/picture-oregon-city-or-bridge-in-fog.JPG)

3. Suspensi
Suspensi is a heterogeneous mixture of particles with a size greater than the 1.10^-7 nm. Example: a mixture of wheat flour with water.

Perubahan Kimia dan Perubahan Fisika

2009-03-19T16:45:00.000-07:00

Perubahan fisika tidak ditandai dengan terbentuknya zat baru. Sedangkan perubahan kimia ditandai dengan terbentuknya zat baru.
Perubahan fisika lebih kita kenal sebagai perubahan wujud zat. Pada perubahan wujud zat, tidak ada zat baru yang terbentuk. Zat tersebut meski telah berubah wujudnya tetapi masih mempunyai rumus molekul kimia yang sama. Macam-macam perubahan fisika:

Mencair: perubahan wujud zat dari padat ke cair.
Menguap: perubahan wujud zat dari cair ke gas.
Menyublim: perubahan wujud zat dari gas ke padat/sebaliknya.
Mengembun: perubahan wujud zat dari gas ke cair.
Membeku: perubahan wujud zat dari cair ke padat.

Perubahan es mencair menjadi air adalah contoh perubahan fisika. Es dan air memiliki rumus molekul sama, yaitu H₂O, sehingga tidak ada zat baru yang terbentuk.

Perubahan kimia kita kenal sebagai reaksi kimia ditandai dengan beberapa ciri:

perubahan warna.
perubahan suhu.
timbulnya endapan.
timbulnya gas.

Pada pembakaran bahan bakar bensin terjadi proses perubahan kimia. Jika bensin kita anggap terdiri dari oktana, terjadi reaksi pembakaran bensin:
C₈H_8(g) + 12 O_2(g) ----> 8 CO_2(g) + 4 H₂O_(g)
bensin + oksigen ----> karbondioksida + uap air
Terlihat bahwa terbentuk zat baru yaitu karbondioksida dan uap air yang memiliki rumus molekul berbeda dengan zat awal yaitu bensin dan oksigen.

============================================================

Physical change is not marked with the new substance. While the chemical changes are marked with the new substance.
Physical change as we know called as phase substance. There is no new substance is created. Although these substance have phase changed but these substance still have the same chemical molecule formula. Various physical changes:

1. Melt: change in form of solid matter to liquid.
2. Evaporate: change in form of liquid matter to gas.
3. Sublimation: change in form of solid matter to gas and vice versa.
4. Dew: change in form of gas matter to liquid.
5. Frozen: change in form of liquid matter to solid.

Changes in ice melt into water is an example of physical changes. Ice and water have the same molecular formula, which is H₂O, so that no new substance is created.

Chemical changes we know as a chemical reaction by a few characteristics:

1. changes of color.
2. changes in temperature.
3. the occurrence of precipitation.
4. the occurrence of gas.

In the combustion of fuel gas there is chemical process change occurs. If we consider gas consists of octane, burning gas reaction:
C₈H_{8 (g)} + 12 O_{2 (g)} ----> 8 CO_{2 (g)} + 4 H₂O _(g)
fuel + oxygen ----> carbon dioxide + water vapor
That form new substances, namely carbon dioxide and water vapor that has a different molecular formula with the initial substances, octane and oxygen gas.

Tentang Atom dan Unsur (About Atoms And Elements)

2009-03-15T15:23:00.000-07:00

Partikel terkecil dari suatu materi disebut atom. Jika kita punya sepotong logam aluminium lalu membaginya menjadi bagian-bagian sangat kecil sehingga tidak dapat dibagi lagi, maka bagian terkecil itu disebut atom.

Unsur adalah jenis/macam atom. Dalam sepotong logam aluminium terdapat banyak unsur aluminium yang bersatu melalui ikatan logam. Dalam air (H₂O) terdapat dua jenis atom, yaitu unsur hidrogen dan oksigen. Jumlah unsur hidrogen = 2 dan jumlah unsur oksigen = 1.
(gambar diambil dari http://www.sciencelearn.org.nz/var/sciencelearn/storage/images/contexts/icy_ecosystems/sci_media/water_molecule/21463-1-eng-NZ/water_molecule_full_size_landscape.jpg)

Kimia menggunakan simbol/lambang untuk mewakili unsur. Simbol/lambang merupakan gambar atau huruf yang digunakan untuk mewakili sesuatu. Kimia menggunakan satu atau dua huruf untuk mewakili unsur. Simbol untuk aluminium adalah Al. Simbol untuk oksigen adalah O dan lain-lain.

Kesimpulannya:
O merupakan unsur karena melambangkan jenis atom oksigen (unsur oksigen).

Atom-atom dapat bergabung membentuk molekul. Ada molekul unsur dan molekul senyawa.
Molekul unsur hanya terdiri dari satu jenis unsur, contoh H₂, O₂, N₂.
Molekul senyawa terdiri dari dua jenis unsur atau lebih, contoh H₂O, NaCl.

Kesimpulannya :
O₂ merupakan molekul unsur, terdiri dari 2 buah atom, jenis atom/unsurnya adalah oksigen.
====================================================================================

The smallest particles of a material called atom. If we have a metal piece aluminum then divide it to the very small parts so it can not be divided again, the smallest part is called atom.

Element is the type of / kind of atom. In aluminium metal piece there are many elements that bond together through the metal. In water (H2O) There are two types of atom, the element hydrogen and oxygen. Number of hydrogen element = 2 and Number of oxygen element = 1.

Chemist using symbols to represent the elements. Symbol is a letter that is used to represent something. Chemical use one or two letters to represent the elements. The symbol for aluminum is Al. The symbol for oxygen is O, and others.

In conclusion:
O is an element because it represents the type of oxygen atom (oxygen elements).

Atom-atom which formed a molecule can join. There are molecular element and molecular compound.
Molecular element consists of only one type of element, for example H2, O2, N2.
Molecular compound consisting of two or more types of elements, eg H2O, NaCl.

In conclusion:
O2 is a molecular element, consist of 2 pieces atom, the type of atom (element) is oxygen.
(picture taken from: http://www.monroecc.edu/depts/pstc/backup/o22.gif)

Kimia Unsur: Hidrogen

2009-03-05T14:49:00.000-08:00

Hidrogen merupakan salah satu unsur kimia yang paling ringan di antara unsur-unsur kimia yang lain. Di atmosfer, hidrogen berada dalam wujud gas diatomik (H₂). Karena massa yang ringan ini, hidrogen di atmosfer hampir tidak dipengaruhi oleh gravitasi bumi sehingga jumlah hidrogen di atmosfer sangatlah langka. Di bumi, hidrogen berada dalam senyawanya seperti senyawa-senyawa hidrokarbon dan gas metana. Gas hidrogen dihasilkan oleh beberapa bakteri dan alga.

(picture taken from: http://keyhole.web.cern.ch/keyhole/theory/hydrogen.jpg)

Secara alamiah, hidrogen memiliki tiga buah isotop, yaitu protium ¹H, deuterium ²H dan tritium ³H. Isotop lainnya tidak stabil mulai disintesis di laboratorium (⁴H sampai dengan ⁷H). Protium merupakan isotop yang paling umum dengan kelimpahan 99,98%. Deuterium berpotensi untuk digunakan sebagai bahan bakar reaktor nuklir komersial. Air berat (air yang kaya deuterium) digunakan sebagai moderator dan pendingin pada reaktor nuklir. Tritium bersifat radioaktif. Sejumlah kecil tritium terbentuk karena interaksi sinar kosmik dan gas atmosfer. Tritium digunakan pada reaksi fusi nuklir dan sebagai perunut isotop kimia bumi.

===============================================================================

Hydrogen is a chemical element that most of the light elements of the other chemicals. In the atmosphere, hydrogen existing in diatomic gas (H2). Because the mass of hydrogen is light, the hydrogen in the atmosphere is almost not influenced by the earth's gravity so that the amount of hydrogen in the atmosphere is very rare. In the earth, the hydrogen found as compounds such as hydrocarbons compounds and methane gas. Hydrogen gas is produced by some bacteria and algae.

Naturally, there is three kinds of hydrogen isotope, protium is ¹H, deuterium ²H, and tritium ³H. Other unstable of hydrogen isotope start synthesized in the lab (4H to ⁷H). Protium is the most common isotope abundance of 99.98%. Deuterium is used as the potential to fuel commercial nuclear reactor. Heavy water (deuterium-rich water) was used as moderators in the refrigerator and the nuclear reactor. Tritium is radioactive. A small amount of tritium was formed of interaction between cosmic rays and the gas atmosphere. Tritium is used in nuclear fusion reactions as tracer and isotope geochemistry.

Membuat CD Pembelajaran Interaktif Menggunakan Flash MX

2009-03-04T14:24:00.000-08:00

Hukum alam selalu berjalan. Bagi yang terbiasa mengalaminya, hukum alam adalah hal yang lumrah. Membuat sebuah media pembelajaran bagi kebanyakan orang mungkin masih merupakan hal yang sulit. Tetapi bagi mereka yang sudah terbiasa menggelutinya, membuat sebuah media pembelajaran bukanlah hal yang sulit.

Pada awalnya saya juga merasa sangat merasa kesulitan. Tetapi saya terus belajar dan belajar, sampai akhirnya saya mendapat sedikit pengetahuan untuk dibagi pada orang-orang yang membutuhkan. Saya berikan sebuah ebook (electronic book) berisi langkah demi langkah untuk membuat sebuah media pembelajaran interaktif lengkap dengan gambar per langkah. Adanya gambar-gambar ini akan memudahkan pemula untuk belajar.

Ebook ini lebih ditujukan pada pemula, tapi bisa juga dipelajari oleh tingkat menengah. Silahkan download di sini.

Download ebook Membuat Media Pembelajaran Interaktif Menggunakan Flash MX.

Unsur Golongan Utama (Golongan A)

2009-02-09T23:19:00.000-08:00

Dalam sistem periodik terdapat unsur-unsur golongan utama (golongan A) dan unsur-unsur transisi (golongan B). Unsur golongan A terdiri dari 44 unsur terbagi atas delapan golongan dari golongan IA sampai dengan golongan VIIIA.

Untuk menghafalkanya gunakan jembatan keledai
Contoh:
Gol IA : HerLi Na Kawin Robin Cs Frustasi

Gol IIA : Bemo Mogok Cari Serep Ban Radial

Silahkan dicari untuk golongan utama yang lain.

Prediksi Kisi-kisi dan Soal Latihan Ujian Nasional Kimia UN 2009

2009-02-07T19:28:00.000-08:00

Lumayan ini ada dua file untuk panduan persiapan ujian nasional kimia 2009 besok. Bagi yang belum pernah download lewat ziddu, ini cara downloadnya:
1. Klik linknya disini (Prediksi Kisi-kisi) atau disini (Prediksi Soal-soal) atau disini (Pembahasan Prediksi Soal-soal). Akan terbuka tab/jendela baru.
2. Muncul tampilan seperti gambar, klik tombol download.

3. Masukkan kode yang tersedia, klik tombolnya, lihat gambar.

Selamat belajar.

Link download:
1. Prediksi Kisi-kisi disini.
2. Prediksi Soal-soal disini.
3. Pembahasan Prediksi Soal-soal disini.

Pembahasan Soal-soal segera menyusul. Pastikan Anda mendapatkan pembahasan soal-soal di atas beberapa hari mendatang.

Pengertian Ilmu Kimia

2009-02-04T13:53:00.000-08:00

PENGERTIAN ILMU KIMIA
Perlu diketahui ilmu kimia adalah ilmu yang mempelajari tentang susunan, struktur, sifat, perubahan serta energi yang menyertai perubahan suatu materi. Materi sendiri adalah sesuatu yang menempati ruang dan mempunyai massa. Jelas bahwa hampir semua benda di alam dibahas dalam ilmu kimia karena pada dasarnya setiap benda menempati ruang dan mempunyai massa. Artinya setiap benda merupakan materi.

APA YANG DIBAHAS DALAM ILMU KIMIA?
Ilmu kimia membahas semua materi tentang:
1. Susunannya dan strukturnya.
2. Sifatnya.
3. Perubahannya.
4. Energi yang menyertai perubahannya.
Misalkan kita membahas "air". Maka secara sederhana yag dipelajari oleh ilmu kimia tentang air adalah mengenai:
1. Bagaimana atom-atom hidrogen dan oksigen tersusun dalam sebuah molekul air dengan membentuk struktur molekul.
2. Bagaimana sifat-sifat air dihubungkan dengan susunan dan struktur tadi.
3. Perubahan apa yang terjadi pada air (erat kaitannya dengan reaksi kimia).
4. Seberapa besar energi yang dihasilkan atau diserap pada perubahan tersebut.

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The CHEMICAL SCIENCE
Please note chemistry is the science of learning about the layout, structure, properties, and the energy changes that accompany the change in a material. The material itself is something that occupies space and has mass. It is clear that almost all objects in the nature discussed in chemistry because basically every object occupies space and has mass. This means that each object is the material.

WHAT CHEMICAL SCIENCE discussed in?
Discusses the chemistry of all materials:
1. Order and structure.
2. Properties.
3. Changes.
4. Energy that accompanies change.
Suppose we discuss the "water". So simply by yag learned about the chemistry of water is about:
1. How-atomic hydrogen and oxygen atoms arranged in a molecule with water molecules form a structure.
2. How is nature connected with the water and the structure of the earlier order.
3. Change what happens to the water (closely related with the chemical reaction).
4. How much energy is produced or absorbed in the changes.

First Posting in 2009

2009-01-01T19:31:00.000-08:00

Now I'm very tired. But I'm very happy. Now I'm employee. Hmm, I feel sad to cause I'll separate my students. I'll miss they. This is my student, the exotic dancer team.

I hope I'll be happy in my new place with my new job.

Atomic Number and Mass Number of Atom (Nomor Atom dan Nomor Massa Atom)

2008-12-27T21:34:00.001-08:00

Every element have a different number of protons. The number of protons is atomic number. Beside protons, in an atom consist of electrons and neutrons. In neutral atom, number of protons is equal to number of electrons. The number of electrons determine the properties of atom.
the number of protons and neutrons which located in nucleuscalled as mass number of atom. The mass of protons and neutrons is atomic mass because the mass of electron is too small, so can be neglected. The atom of an element expressed by the following symbol:

where:
X = the symbol of atom
A = mass number of atom
Z = atomic number
Example: the symbol of C atom given by , so:
mass number of atom = A = the number of protons and electrons = 12
atomic number = the number of protons = the number of electrons = 6
the number of neutrons = A - Z = 12 - 6 = 6

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Setiap atom memiliki jumlah proton yang berbeda. Jumlah proton yang kita sebut sebagai nomor atom. Selain proton, di dalam atom juga terdapat elektron dan neutron. Dalam atom netral, jumlah proton sama dengan jumlah elektron. Jumlah elektron inilah yang menentukan sifat-sifat suatu atom.
Jumlah proton dan neutron yang terletak dalam inti atom disebut sebagai nomor massa atom. Massa proton dan neutron dianggap sebagai massa atom karena massa elektron terlalu kecil sehingga dapat diabaikan. Atom suatu unsur biasanya dilambangkan sebagi berikut:

dimana:
X = lambang atom
A = nomor massa atom
Z = nomor atom
Contoh: atom C memiliki lambang , maka:
nomor massa = A = jumlah proton dan neutron = 12
nomor atom = jumlah proton = jumlah elektron = 6
jumlah neutron = A - Z = 12 - 6 = 6

Isotope, Isobar and Isoton (Isotop Isobar dan Isoton)

2008-12-27T04:33:00.000-08:00

Jika kita berbicara tentang massa atom relatif dan nomor atom, ada tiga konsep penting yang harus kita ketahui, yaitu isotop, isobar dan isoton.

1. Isotop
Isotop adalah dua atom atau lebih atom unsur yang memilki nomor atom sama tetapi nomor massanya berbeda. Contoh:
, dan adalah isotop karbon.
dan adalah isotop nitrogen.
2. Isobar
Isobar adalah dua atau lebih atom unsur yang memiliki nomor massa sama tetapi nomor atomnya berbeda. Contoh:
dan adalah isobar.
dan juga merupakan isobar.
3. Isoton
Isoton adalah dua atau lebih atom unsur yang memiliki nomor atom dan nomor massa berbeda tetapi jumlah neutronnya sama. Contoh:
(n = 12 - 6 = 6) dan (n = 13 - 7 = 6)adalah isoton
(n = 13 - 6 = 7) dan (n = 14 = 7 = 7) juga merupakan isoton.

If we talk about relative atomic mass, there are three important concepts which must be known, those are isotope, isobar and isoton.
1. Isotope
Isotope is two or more element atoms having the some atomic number but differing in mass number. Example:
, and are carbon isotopes.
and are nitrogen isotopes.
2. Isobar
Isobar is two or more element atoms having the same mass number but differing in atomic namber. Example:
and are isobar.
and are isobar too.
3. Isoton
Isoton is two or more element atoms differing in atomic number and mass atom, but having the same number of neutrons.Example:
(n = 12 - 6 = 6) and (n = 13 - 7 = 6) are isoton
(n = 13 - 6 = 7) and (n = 14 = 7 = 7) are isoton too.

About Google Search

2008-12-26T05:27:00.002-08:00

Usually we just using google to search document or anything we need. In fact google have a lot of excess which almost never been used. Ok, let's playing with google.

If we want to know the weather in a place, we just type weather [place] at input box. Then google will show you the weather information in that city. For example, we type weather Jakarta, will be result here.

To see the time, you just need to type time [place]. Fore example time Jakarta will result.

If we want to see the score match of a sport game, type [club]. Example Juventus will be result.

Selama ini google lebih sering atau bahkan selalu kita gunakan untuk mencari sesuatu yang kita butuhkan di web. Ternyata, google mempunyai banyak kelebihan yang jarang atau bahkan hampir tidak pernah kita gunakan. OK, kita bisa bermain-main sebentar dengan google.

Jika Kita ingin mengetahui cuaca di suatu tempat tinggal kita ketik weather [nama tempat] di kotak input. Maka akan ditunjukkan informasi cuaca di kota tersebut, misalnya kita ketik weather Jakarta, akan muncul hasilnya seperti gambar.javascript:void(0)

Untuk melihat waktu, kamu tinggal ketik time [nama kota]. Contoh time Jakarta. Hasilnya:

Jika kamu ingin melihat skor pertandingan olahraga ketik [klub]. Contoh Juventus, hasilnya

PPM (Part Per Million) atau BPJ (Bagian Per Juta)

2008-12-16T15:37:00.000-08:00

Ppm merupakan salah satu ukuran kadar suatu zat dalam campurannya. Ppm (part per million) dalam bahasa Indonesia diterjemahkan sebagai bpj (bagian per juta). Dari pengertiannya kita bisa mengambil kesimpulan bahwa ppm atau bpj merupakan kadar beberapa bagian zat dalam satu juta sistem.

Pada gambar air sungai di samping, misalkan dari hasil penetian kandungan timbalnya adalah 4 ppm (bisa juga dikatakan 4 bpj), berarti bahwa dalam 1 kg air sungai terdapat:
(4/1.000.000) x 1 kg timbal
= 0,000004 kg timbal
= 0,004 gram timbal
= 4 mg timbal.

Ppm atau bpj biasanya digunakan jika zat yang terkandung dalam suatu sistem campuran jumlahnya sangat sedikit. Misalkan jika terdapat 10 gram gula dalam 100 gram larutan gula, kadar zat dinyatakan dalam persen. Dalam contoh ini kadar gula dalam larutan gula adalah
(10/100) x 100%
= 10%

Semoga bermanfaat.

Pernik Koloid

2008-06-13T14:09:00.000-07:00

Aplikasi gelatin dalam industri pangan sangat luas. Fungsi utama gelatin di dalam industri ini adalah untuk meningkatkan elastisitas, konsistensi dan stabilitas produk pangan yang dihasilkan. Gelatin digunakan untuk produk-produk dessert, produk-produk dari susu (dairy products) seperti youghurt, krim asam, keju. Begitu juga dengan es krim, pie krim serta kue keju (cheese-cakes). Gelatin juga merupakan bahan utama dalam pembuatan produk marshmallows, disamping juga digunakan secara meluas untuk produksi toffees dan margarin.
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Zat besi dalam makanan memasuki saluran pencernaan dalam bentuk feros hidrosida koloid. Zat besi dalam bentuk koloid ini tidak dapat diserap tubuh secara langsung. Ia harus melalui peran getah lambung barulah dapat diserap melalui tubuh. Asam tanat dalam teh sangat mudah bersenyawa dengan zat besi dan membentuk asam tanat feros larut yang merintangi penyerapan zat besi. Bila tubuh orang yang kurang darah kekurangan zat besi, hemoglobin sintetis dalam tubuh bisa berkurang, dan penyakitnya bisa bertambah parah.
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Kelenjar tiroid adalah kelenjar yang terdiri dari 2 lobus dan terdapat pada leher bagian depan di bawah jakun. 2 lobus ini dihubungkan oleh istmus. Kelenjar tiroid terdiri dari sel epitel kubus yang membentuk struktur bernama vesikel dan ditunjang oleh suatu jaringan penghubung. Pada kelenjar tiroid normal, vesikel ini berisi substansi koloid yaitu protein yang bernama thyroglobulin yang dikombinasikan dengan tiroksin.

Pembuatan Aspirin

2008-05-05T09:26:00.000-07:00

I.TUJUAN
Setelah menyelesaikan eksperimen ini mahasiswa diharapkan dapat :
1.Menjelaskan reaksi esterifikasi yang terjadi pada senyawa asam salisilat.
2.Terampil dalam cara kerja pembuatan dan pemurnian aspirin dari asam salisilat.
3.Terampil dalam cara kerja dan teknik-teknik kristalisasi zat organik.
II.LANDASAN TEORI
Awalnya terinspirasi oleh sakit artritis yang diderita ayahnya, Hoffmann, seorang berkebangsaan Jerman mensintesis suatu senyawa bernama asam asetil salisilat (aspirin). Dengan senyawa ini Hoffmann dapat mengobati ayahnya tanpa mengakibatkan iritasi perut yang parah seperti efek samping obat artritis pada masa itu. Itulah salah satu fungsi aspirin yang dicobakan pada praktikum ini. Fungsi aspirin lainnya adalah sebagai pereda demam dan meringankan reumatik.
Aspirin dibuat dengan mereaksikan asam salisilat dengan anhidrida asam asetat menggunakan katalis H2SO4 pekat sebagai zat penghidrasi. Asam salisilat adalah asam bifungsional yang mengandung dua gugus –OH dan –COOH. Karenanya asam salisilat ini dapat mengalami dua jenis reaksi yang berbeda. Dengan anhidrida asam asetat akan menghasilkan aspirin, sedangkan dengan metanol ekses akan menghasilkan metil salisilat.

Aspirin yang terjadi dapat bereaksi dengan NaHCO3 membentuk garam natrium yang larut dalam air, sedangkan hasil samping berupa polimer tidak larut dalam bikarbonat. Perbedaan sifat ini digunakan untuk pemurnian aspirin.

Kita bisa menggunakan besi(III)klorida untuk menguji kemurnian aspirin. Besi(III)klorida bereaksi dengan gugus fenol membentuk kompleks ungu. Asam salisilat (murni) akan berubah menjadi ungu jika FeCl3 ditambahkan, karena asam salisilat adalah fenol. Jika tidak ada gugus fenol warna larutan tak berubah (kuning).
III. ALAT DAN BAHAN
Alat : Erlenmeyer 250 cc 2 buah, gelas ukur 20 cc dan 100 , termometer 100C, corong hisap lengkap, penangas air, pipet tetes, pengaduk dan benzena untuk rekristalisasi.
Bahan : Asam salisilat 1 gram, anhidrida asam asetat 2,5 ml,asam sulfat pekat 3 tetes dan akuades.
IV.CARA KERJA
A. PEMBUATAN

B. PEMURNIAN

C. REKRISTALISASI

V. DATA PENGAMATAN
Percobaan.
Pengamatan
A.PEMBUATAN
1 g as salisilat + 2,5 ml as cuka anhidrida, Larutan putih keruh
+ 2,5 ml H2SO4 -----> goyangkan, Kuning kotor
panaskan ± 10 mnt (50-60°C) sambil diaduk, Endapan putih
dinginkan (sewaktu-waktu diaduk), sedikit larutan
+ 75 ml akuades, larut sebagian
aduk, larut
saring dengan saringan hisap, filtrat jernih

B.PEMURNIAN
aspirin tak murni + NaHCO3 jenuh, terbentuk gelembung gas
aduk sampai reaksi sempurna, larut (jernih)
saring dengan saringan hisap ….(filtrat), filtrat
1,75 ml HCl pekat + 5 ml air, larutan jernih
+ filtrat (aduk), endapan putih
dinginkan dengan es, kristal (sedikit larutan)
saring dengan Buchner, kristal murni
cuci kristal dengan air es dingin, kristal lebih murni
taruh di gelas arloji, kristal kering

C.REKRISTALISASI
larutkan kristal dalam benzena, larut
panaskan dengan penangas, larut (jernih)
saring, filtrat
keringkan di oven, terbentuk kristal murni = 0,06 g

VI. PERHITUNGAN
Dalam percobaan digunakan asam salisilat sebanyak 1 g, sehingga mol asam salisilat dapat dihitung, yaitu 1/138 = 0,007 mol. Reaksinya adalah sbb :

Aspirin yang dihasilkan dapat dihitung secara teoritis yaitu mol aspirin dikalikan dengan Mr-nya. Mol aspirin = mol asam salisilat = 0,007 mol. Gram aspirin secara teoritis adalah 0,007 x 180 = 1,26 gram. Dari percobaan dihasilkan aspirin sebanyak 0,06 g, maka rendemennya :
(massa hasil percobaan/massa teoritis) x 100% = (0,06/1,26) x 100% = 4,8%.

VII. PEMBAHASAN
Pada pembuatan aspirin aspirin ini mula-mula dicampurkan 1 g asam salisilat dengan anhidrida asam asetat. Reaksi yang terjadi adalah reaksi esterifikasi yang merupakan prinsip dari pembuatan aspirin. Reaksi esterifikasi tersebut dapat dijelaskan sebagai berikut.

Ester dapat terbentuk salah satunya dengan cara mereaksikan alkohol dengan anhidrida asam. Dalam hal ini asam salisilat berperan sebagai alkohol karena mempunyai gugus –OH, sedangkan anhidrida asam asetat tentu saja sebagai anhidrida asam. Ester yang terbentuk adalah asam asetil salisilat (aspirin). Gugus asetil (CH3CO-) berasal dari anhidrida asam asetat, sedangkan gugus R-nya berasal dari asam salisilat (pada gambar di atas gugus R ada di dalam kotak). Hasil samping reaksi ini adalah asam asetat.
Langkah selanjutnya adalah penambahan asam sulfat pekat yang berfungsi sebgai zat penghidrasi. Telah disebutkan di atas bahwa hasil samping dari reaksi asam salisilat dan anhidrida asam asetat adalah asam asetat. Hasil samping ini akan terhidrasi membentuk anhidrida asam asetat. Anhidrida asam asetat akan kembali bereaksi dengan asam salisilat membentuk aspirin dan tentu saja dengan hasil samping berupa asam asetat. Jadi, dapat dikatakan reaksi akan berhenti setelah asam salisilat habis karena adanya asam sulfat pekat ini.
Tetapi harus diperhatikan bahwa sebelum dipanaskan, reaksi tidak benar-benar terjadi. Reaksi baru akan berlangsung dengan baik pada suhu 50-60°C. Juga pada percobaan ini baru terbentuk endapn putih (aspirin) setelah dipanaskan. Kemudian endapan tersebut dilarutkan dalam air dan disaring untuk memisahkan aspirin dari pengotornya. Tetapi tentu saja dengan penyaringan ini aspirin yang dihasilkan belum benar-benar murni.
Untuk pemurnianya, aspirin tak murni kemudian ditambahi larutan NaHCO3. Reaksinya adalah sebagai berikut :

Aspirin akan larut, sedangkan hasil sampingnya tidak larut, sehingga ketika disaring akan didapatkan filtrat aspirin murni berbentuk larutan jernih. Larutnya aspirin ini juga diikuti oleh timbulnya gelembung gas CO2, membuktikan adanya hasil reaksi aspirin dengan NaHCO3. setelah itu filtrat diaduk dan terbentuk endapan putih. Lalu didinginkan dengan air es membentuk kristal. Kristal akan lebih murni setelah dicuci dengan air es. Selanjutnya kristal dikeringkan dengan cara ditaruh di gelas arloji dan didapatkanlah kristal kering.
Langkah terakhir pada percobaan ini adalah rekristalisasi. Kristal yang kering tadi dilarutkan dalam benzena panas, alu dipanaskan. Benzena digunakan sebagai pelarut karena benzena merupakan pelarut yang baik untuk zat organik. Air tidak bisa digunakan untuk rekristalisasi ini karena air adalah pelarut polar dan aspirin adalah senyawa nonpolar. Setelah itu larutan tadi disaring panas-panas dan filtratnya diambil untuk dikeringkan di oven. Kristal ini merupakan kristal yang benar-benar murni.
Hasil percobaan ini diperoleh aspirin sebanyak 0,06 gram. Hasil ini sangat sedikit karena menurut perhitungan, rendemennya hanya 4,8%. Berkaitan dengan hasil yang minim ini ada beberapa hal yang perlu dibahas disini, yaitu :
1.Benzena yang digunakan untuk rekristalisasi suhunya kurang panas, tetapi hangat.
2.Ketika dilakukan pengeringan di oven, tidak diberi tanda kelompok (hanya diingat tempatnya) sehingga ada (sangat sedikit sekali) kemungkinan kristal diambil kelompok lain.
3.Jika nomor dua tidak terjadi, berarti hasil penyaringan yang berjumlah banyak tidak jadi *.
VIII.KESIMPULAN
1.Aspirin dapat dibuat dengan mereaksikan asam salisilat dengan anhidrida asam asetat dengan adanya H2SO4.
2.Prinsip pembuatan aspirin adalah reaksi esterifikasi.
3.Pelarut organik (seperti benzena) dapat digunakan untuk rekristalisasi senyawa organik.
4.Diperoleh rendemen sebesar 4,8%.
IX.DAFTAR PUSTAKA
Ralp J. Fessenden, Joan S. Fessenden, 1990, Kimia Organik 3rd Edition, Penerbit Erlangga : Jakarta.
Drs. Ersanghono Kusuma, MS, 2003, Sintesis Organik, Jurusan Kimia FMIPA UNNES : Semarang.
Tim Dosen, 2003, Diktat Petunjuk Praktikum Kimia Organik 2, Lab. Kimia FMIPA UNNES : Semarang.
http://homepage.ius.edu/DSPURLOC/C122asp.htm.
http://home.snu.edu/dept/chemistry/syillabi/ARCHIVES/CHEM11~1/Labs__~1/ SYNTHE~1.DOC.

Semarang, 30 April 2003
Praktikan

Ari Hendriayana

* Penyaringan terakhir (rekristalisasi) dilakukan dua kali. Yang pertama menghasilkan endapan yang banyak dan penyaringan kedua hasilnya sedikit. Tetapi yang jadi kristal alah yang kedua, sementara hasil penyaringan pertama (yang sedikit) tidak jadi.

Study Tour Part 4: Back Home

2008-03-21T23:17:00.000-07:00

Di rumah makan kami menghabiskan waktu cukup lama. Karena waktu semakin sore, anak-anak mengira ga mungkin ke Borobudur, pasti langsung ke Malioboro. Mereka pun berinisiatif sendiri memoles diri mereka seganteng dan secantik mungkin. Maklum, Malioboro adalah dua tempat yang paling ditunggu-tunggu. Sayang, karena bisnya mogok perjalanan ga mungkin dilanjutkan. Daripada dandanan mereka sia-sia, tak ada salahnya mereka diabadikan ke dalam kamera. Ide bagus juga ketika salah satu rekan guru menyuruh saya untuk memotret anak-anak. Jadilah saya fotografer dadakan. Namanya juga fotografer dadakan, hasilnya pun kacau. Tapi ada dua foto yang kualitasnya bagus, ini dia.

Syukurlah, meskipun perjalanan tidak dilanjutkan dan kami kembali ke Semarang, anak-anak bisa memahami kalo bisnya mogok perjalanan tak mungkin dilanjutkan. Saya pun menyusuri jalanan Magelang Semarang dengan sepeda motor. Senja yang melelahkan. Sampai di sekolah saya menunggu rombongan bis. Seneng rasanya melihat anak-anak tetap ceria dan tetap semangat meski acara hari itu kurang sempurna.

Study Tour Part 3: Time to Eat

2008-03-21T22:34:00.000-07:00

Akhirnya waktu yang ditunggu-tunggu datang juga. Waktunya makan. Di sebuah runah makan yang memang biasa digunakan khusus untuk rombongan yang sedang berwisata. Lumayan enak juga menunya mengingat perut yang cukup lapar. Mari makan bareng-bareng.

Eh, ada yang ketinggalan ternyata. Satu rombongan masih di perjalanan. Rupanya ada halangan. Oke dech kami tunggu. Nah, itu datang. Ayo yang baru datang makan dulu. Ini salah satu yang baru datang. Laper atau rakus ya...?

Study Tour Part 2: At The Theatre

2008-03-21T21:41:00.000-07:00

In Ketep there is a theatre. We enter the theatre to watch a movie about Merapi. We found a lot of information here, especially abot Merapi. Unfortunately, I don't bring any papers to wrote thats information. Then..... Duh, susahnya bahasa Inggris. Kemudian kami menghabiskan waktu untuk foto-foto.

That's pic in front of theatre At 1:00 we exit from Ketep to go to restaurant.

Study Tour Part 1: Going to Ketep

2008-03-21T20:34:00.000-07:00

Hari Kamis kemarin kebetulan tanggal merah dan libur bersamaan dengan hari Jumat esok harinya. Sekolahku mengadakan study tour ke Yogya. Walaupun badan cape dan butuh istirahat, mumpung gratis ikut dech. Sayangnya, biarpun udah disiapin aku bangunnya telat sampe ketinggalan bis. Kepalang tanggung, nyusul dech pake motor.

Melalui perjuangan yang cukup melelahkan akhirnya sampai juga di Ketep lebih dulu. Sempat nyasar dua kali karena salah ambil tikungan. Sok pede gitu ga nanya orang dulu. Dari Ketep kita bisa melihat puncak Merapi dari dekat. Bagus juga kan gambarnya. Untung datang lebih dulu, kalo agak siang pasti berkabut dan gunungnya ga keliatan. Tapi ga tau kenapa, udaranya di sana panas banget. Namun, begitu masuk ke dalam mushola yang ada di sana, hawanya jadi sejuk. Sempat ketemu dan ngobrol sama cewek cantik juga di sana. Malangnya Pak Tovik dan rombongan keburu datang sehingga saya harus bergabung dengan rombongan yang pake bis.

Oxidation Number

2008-01-19T22:10:00.000-08:00

The rule of oxidation number:

Oxidation number for neutral substance just contains one element = 0. For example, O₂ = 0, S₈ = 0.
Oxidation number F = -1.
3. Metal IA = +1. IIA = +2. IIIA = +3. Ag = +1. Zn = +2. Other metals have more than one oxidation number.
Hydrogen = +1 except in: Metal hydride = -1. NaH --> oxidation number of H = -1.
5. Oxygen = -2, except in: OF₂ = +2. Peroxyde (Ex:H₂O₂) = -1. Superoxyde (Ex: KO₂)= -1/2.
The sum of oxidation number in a neutral compounds is zero. In H₂SO₄ compuond: H = +1 O = -2 S = +6 2H + S + 4O = 2.(+1) + (+6) + 4.(-2) = 0.
Simple ionic compounds have oxidation number equal to the charge on the ion. Oxidation number of Na⁺ = +1. Oxidation number of S^2- = -2.
The sum of oxidation number in ionic compounds is equal to the charge on the ionic compound. At NH₄⁺ oxidation number of H = +1 and N = -3. Sum = N + 4H = (-3) + 4.(+1) = +1.

History of Atom Models

2007-07-28T17:40:00.000-07:00

If we talk about the history of atom, we can separate this into two periode, classic and modern. At the classic periode we find Democritus and Aristoteles. Aristoteles think that a matter have discontinue properties. If us divide a matter, hence we can continue the dividing of infinite. While according to Aristoteles, we will until in the situation that matter is other impartible. The impartible matter at later was called atom by Dalton.

The next person who released atom model theory is Dalton. He say that atom like ball of bilyard. One otem and another have different in form and properties. Chemical reactions are rearrangements of atoms (mass is conserved). Then Thomson continue idea concerning atom with the theory of that atom is positive electricity particle and electron spread over in it.

At next period, Rutherford release Solar System Model. Having taken steps attempt shot off alpha rays to a gold plate, he find that shot off alpha rays continued, to be turned and re-bounced. From this experiment result Rutherford trigger the idea of concerning atomic nucleus. Electron reside in around nucleus like our solar system with atomic nucleus as his center.

Next model of the atom conceived by Danish physicist Niels Bohr in 1913. It assumes that the following rules govern the behaviour of electrons: (1) electrons revolve in orbits of specific radius around the nucleus without emitting radiation; (2) within each orbit, each electron has a fixed amount of energy; electrons in orbits farther away from the nucleus have greater energies; (3) an electron may ‘jump’ from one orbit of high energy to another of lower energy causing the energy difference to be emitted as a photon of electromagnetic radiation such as light; (4) an electron may absorb a photon of radiation and jump from a lower-energy orbit to a higher-energy one.(http://encyclopedia.farlex.com)

Electrons are in constant motion around the nucleus, protons and neutrons jiggle within the nucleus, and quarks jiggle within the protons and neutrons.

This picture is quite distorted. If we drew the atom to scale and made protons and neutrons a centimeter in diameter, then the electrons and quarks would be less than the diameter of a hair and the entire atom's diameter would be greater than the length of thirty football fields! 99.999999999999% of an atom's volume is just empty space!(http://particleadventure.org)

I have no more idea to explain you about this topic. If you have a good knowledge about history of atoms theory, I hope you can tell me.

Asian Cup 2007: Good Effort Indonesia, Excellent Vietnam

2007-07-23T18:45:00.000-07:00

Today, I have no work. I just have three day work at my office. Then I remember my football national team. They have been battle with Bahrain (2-1), Saudi Arabia (1-2) and South Korea (0-1). Although they have failed to reach quarter final, they have made very entertained show, especially when battle against Saudi Arabia. At this match, the referee from Uni Emirat Arab have very bad job, so embarassed. But, it's was showed that Indonesian National Team have a good prospect to future. The manager, Ivan Venko Kolev (Bulgaria) pens new deal. He made good job.

In other side, another national team from south east Asia, Vietnam, have an excellent job. They was qualified for quarter final before hammered by Irak. In future I'm sure they will growth become good team and increase their level. What was happened in this Asian Cup is a fact and has to accepted. The Socceeroes, Australia have been knocked out by holder, Japan.

Now, just four team who have reached semifinal. Japan will battle against Saudi Arabia and South Korea against Irak. We are waiting for a champion in Asian Cup.

Indonesia Win

2007-07-11T09:20:00.000-07:00

Last tuesday Indonesia host was happy properly. Pass the venomous struggle, national team of Indonesia finally can defeat the Bahrain 2-1. Team which initialy is not exeeded prove that spirit of nationalism can alter the whoever prediction. There is still two match to Indonesia host that is against Saudi Arabia and South Korea. Both of them same heavy.

But, at least, victory from Bahrain improve the player moral. Walke to reach for the goals to quarterfinal have opened. Is expected by tons of supporter as twelveth player can make the Indonesia incise the better achievement. If arrest to hold on draw with Saudi Arabia and South Korea or win one of them, hence quarterfinal have on-hand.

Beside result of seething with excitement to this host, of course there is one matter which must fixed we hold high that is sportivity and spirit of togetherness. Vigorously, dream to parallel with the european countries is ready to realized by yellow race, Asian.

Leave the Cigarettes

2007-07-06T22:16:00.000-07:00

This afternoon I still can't leave my bad habit. I'm a smoker. I know that cigarette full of toxic. Ciggarette contains about 4000 kinds of toxic in little composition. But, if the cigarettes consumed at long time, the toxics will cumulated in our body. The toxic will disturb function vital organ in our body.

The toxin like nikotin, TAR, naphtalena etc. can cause many diseases like cancer, TBC and respiration function. If we having ilness, smoking habit is not a comfortable activity. This time, I don't interest by cigarettes. I'm having cold. But, as a smoker, tomorrow I can certain that I'm won't smoking. I feel I'm just not smoking if I'm not health.

For you, who haven't smoking, don't want to try smoke cause you will be like me, can't leave the cigarettes. Cigarettes is integral part of my life.

(picture taken from www.everestuncensored.org)

Nanotechnology: Really Just Happen in My Dream

2007-07-05T09:37:00.000-07:00

I am a student of the chemical route. Unfortunately I'am not attracted by science. At one time my lecturer told about new technology that makes me increasingly pessimistic with my capacity in the scientific field. We call it nanotechnology. What is the meaning of nanotechnology? A nanometer is a unit of spatial measurement that is 10^-9 meter, or one billionth of a meter. I don't know nanotechnologi definitely. I think nanotechlogy is a technology with supported by measurement unit of 10^-9.

My teacher say that atoms diametre is about nanometre size. It means, using nanotechnology We can cut and organise the atoms in accordance with our wish. We can build any compound. World won't be deficient from another needs. So, what will you do? Do you will build science based by nanotechnology or just waiting like me?

(picture taken from http://www.imm.org/)