A 11.0g sample of compound containing only oxygen and carbon produces 3.0g carbon and 8.0g oxygen. Determine the empirical formula of the compound.

3 answers

3g C = 1/4 mole
8g O2 = 1/2 mole

So, you have CO2
CxOy ==> xC + 1/2O2

% C = (3/11)*100 = ? about 27
% O2 = (8/11(*100 = about 73

mols C = about 27/12 = about 2.25
mols O2 = about 73/32 = about 2.28 O2 molecules or about 4.56 mols O atoms.

Now find the ratio of the C atoms to the O ATOMS, round to whole numbers and that will be the empirical formula. The easy way to find the ratio is to divide the smaller number by itself (which makes it 1.00), then divide the other number by the same small number.
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