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

2 komentar:

Anne Leah said...

When I was still in HS, I really find Chem so hard. I think many people would think so too. It' s a tough topic that needs more focus. high school chem/high school chemistry tutoring could help out with that.

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