Asked by jason
A sample of acid (C,H,O) massing 1.000 g burns to give 1.466 g of carbon dioxide and 0.6001 g of water. The molecular mass is approximately 120 g/mol. Calculate the molecular formula of the acid
Answers
Answered by
DrBob222
Determine percent C, H, and O.
mols CO2 = 1.466/molar mass CO2.
mols H2O = 0.6001/molar mass H2O.
Convert mols CO2 to mols C, then to g C, then %C= g C/1.000 g sample.
Convert mols H2O to mols H, then to g H, then to %H.
Find %O by 100-%C-%H.
Then take a 100 g sample which will give you the g C, H, and O.
Divide each by atomic mass, find the ratio of th three with small whole numbers, this will give you the empirical formula.
120/empirical formula mass = a number, n and the molecular formula = (empirical formula)<sub>n</sub>
Post your work if you get stuck.
There is a slightly shorter way of doing this but it's harder for me to explain it that way.
mols CO2 = 1.466/molar mass CO2.
mols H2O = 0.6001/molar mass H2O.
Convert mols CO2 to mols C, then to g C, then %C= g C/1.000 g sample.
Convert mols H2O to mols H, then to g H, then to %H.
Find %O by 100-%C-%H.
Then take a 100 g sample which will give you the g C, H, and O.
Divide each by atomic mass, find the ratio of th three with small whole numbers, this will give you the empirical formula.
120/empirical formula mass = a number, n and the molecular formula = (empirical formula)<sub>n</sub>
Post your work if you get stuck.
There is a slightly shorter way of doing this but it's harder for me to explain it that way.
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