Monday, October 31, 2011

Percent Composition by Mass

Percent always allows us to compare a part of something to the whole.
In general
% = part x 100
total
For percent composition
% = total mass of particles requested x 100
molar mass

Example: Determine the % oxygen in sulfuric acid.
% O =       4 oxygen          x 100
(2 H + 1 S + 4 O)

%O =               4(16.0) ___  _  x 100 = 48.9% O
                                                         2(1.0) + 32.1 + 4(16.0)

Example: Determine the % sulfate in sulfuric acid.
%SO4 =               32.1 + 4 (16.0)___  _  x 100 = 97.9% O
                                                            2(1.0) + 32.1 + 4(16.0)

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