Empirical formula

Question

When a 35.07 g sample of phosphorus reacts with oxygen, a 71 g sample of phosphorus oxide is formed. What is the percent composition of the compound? What is the empirical formula for this compound? 

Answer 1

71g - 35.07g = 35.93 g of oxygen

 

Percent composition is:

 

Phosphorus: 35.07/71= 49.4%

Oxygen: 35.93/71 = 50.6%

 

 

Find the number of moles of phosphorus and oxygen

 

phosphorous : 35.07g / 31 g/mol = 1.13 mol

oxygen : 35.93 / 16g/mol = 2.25 mol

 

divide by the smallest:

 

1.13/1.13 = 1

2.25/1.13= 2

 

Empirical formula is: PO₂