A 0.50 g sample of a pure substance contains 0.40 g C and 0.10 g H. What is the empirical formula of this compound?

Question

Quizplus · Accepted Answer

To find the empirical formula, we need to determine the mole ratio of the elements. 
The number of moles of carbon can be calculated as: 
0.40 g C x (1 mole C/12.01 g) = 0.033 mol C 
The number of moles of hydrogen can be calculated as: 
0.10 g H x (1 mole H/1.01 g) = 0.099 mol H 
We then divide both by the smaller value, which is 0.033:
0.033 mol C / 0.033 = 1 mol C 
0.099 mol H / 0.033 = 3 mol H 
This gives us a mole ratio of 1:3 for C:H. 
The empirical formula therefore has one carbon atom and three hydrogen atoms, which can be written as CH3. 
The correct choice is B, which gives this formula.

A 050 G Sample of a Pure Substance Contains 0