## Tuesday, 25 December 2012

### Calculate the Molecule Mass Relative of the Compound

Molecular mass relative (Mr) calculated from the atomic mass number (Ar) of the elements in the molecule. Ar express the weight of the element relative to 1/12 atomic mass of C-12 isotope. Here is the example of the Mr NaCl calculation.

Since Ar Na=23 and Ar Cl=35,5

so, Mr NaCl is equal to the sum of that:
Mr NaCl = (1 x Ar Na) + (1 x Ar Cl) = (1 x 23) + (1 x 35,5) = 23 + 35,5 = 58,5

Now, you have to able to calculate the amount of Mr H2SO4 while known that Ar H = 1, Ar S = 32 and Ar O = 16. Right, the answer below.
Mr H2SO4 = (2 x Ar H) + (1 x Ar S) + (4 x Ar O) = (2 x 1) + (1 x 32) + (4 x Ar 16) = 2 + 32 + 64 = 98

The value of atomic mass number of some elements shown below.
H = 1        Li = 7        Mg = 12
C = 12      Na = 23      Ca = 40
O = 16      K = 39        Fe = 56
N = 14      Cl = 35,5    Cu = 63,5

## Saturday, 22 December 2012

### Acid Overview

An acid simply defines as a substance in water solutions dissociate yielding hydrogens ions as only a positive ions. Some acids dissociate in one step yield one hydrogen ion called monobasic acid. Here is the example monobasic acid.

Others acid dissociate yield two or more hydrogen ions through two dissociation steps or more called polybasic acid.

Actually, in a aqueous solution, hydrogen ions doesn't exist. This proton combine with a water molecule form a hydronium ions by coordination covalent bond using a free pair electron from oxygen of the water molecule.