An organic compound contains 60.0% carbon, 4.44% hydrogen and the remainder oxygen. It has a molecular weight of 180. Determine the empirical formula of the compound.

Question

Quizplus · Accepted Answer

1) Find the mass of carbon: 
60.0% of 180 = 108 g 
2) Find the mass of hydrogen: 
4.44% of 180 = 8.0 g 
3) Find the mass of oxygen: 
180 - 108 - 8.0 = 64.0 g 
4) Calculate the number of moles of each element: 
a. Carbon: 108 g / 12.01 g/mol = 9.00 mol 
b. Hydrogen: 8.00 g / 1.01 g/mol = 7.92 mol 
c. Oxygen: 64.0 g / 16.00 g/mol = 4.00 mol 
5) Divide by the smallest number of moles to get the simplest ratio: 
a. Carbon: 9.00 mol / 4.00 mol = 2.25  
b. Hydrogen: 7.92 mol / 4.00 mol = 1.98 
c. Oxygen: 4.00 mol / 4.00 mol = 1.00 
6) Multiply all by 4 to get the empirical formula: 
a. 2.25 x 4 = 9 
b. 1.98 x 4 = 8 
c. 1.00 x 4 = 4 
Empirical formula: C9H8O4 
Therefore, the best choice is C.

An Organic Compound Contains 60