Question

A compound contains 10.13% C and 89.87% Cl (by mass). Determine both the empirical formula and the molecular formula of the compound given that the molar mass is 237 g/mol.

CCl3
C2Cl
CCl

Answer 1

In a 100 g sample of the compound, there are 10.13 g of C and 89.87 g of Cl. Therefore, in a 100 g sample, there are

and

Therefore, the ratio of Cl to C in a sample of the compound is

which is close enough to 3. Thus, the empirical formula of the compound is CCl₃. The molar mass of the compound is 237 g/mol. The molar mass of CCl₃ is 118.37 g/mol. 237 g/mol is roughly double the molar mass of CCl₃. Just multiply the coefficients of the empirical formula by 2 and you get the chemical formula of the compound, CCl₆.

Hope this helps!