An unknown acid has a molar mass of 60.05 g/mol.Given the following percent composition,what is the molecular formula? 40% C,6.7% H,53.3% O

Question

Quizplus · Accepted Answer

First, we need to determine the empirical formula by converting the percent composition to moles: 
C: (40 g) / (12.01 g/mol) = 3.33 mol 
H: (6.7 g) / (1.01 g/mol) = 6.63 mol 
O: (53.3 g) / (16.00 g/mol) = 3.33 mol

Dividing by the smallest number of moles (3.33), we get the empirical formula: 
CH2O

To find the molecular formula, we need to know the molar mass. Since the molar mass given is close to 60.05 g/mol, we can assume that the empirical formula has a molar mass close to 60.05 g/mol. The empirical formula has a molar mass of 30.03 g/mol, which means we need to double the subscripts in the empirical formula to get a molar mass close to 60.05 g/mol.

The molecular formula for this unknown acid is C2H4O2, which has a molar mass of 60.05 g/mol. Choice C matches this molecular formula.

An Unknown Acid Has a Molar Mass of 60