Question

A compound is 44.7% P and the rest O. Determine its emperical formula.

Answer 1

Answer:  

P₅O₁₂

Explanation:  

Assume that you have 100 g of the compound.  

Then you have 44.7 g P and 55.3 g O.  

1. Calculate the moles of each atom  

Moles of P  = 44.7 × 1/30.97 = 1.443 mol Al  

Moles of O = 55.3 × 1/16.00 = 3.456 mol O  

2. Calculate the molar ratios.  

P: 1.443/1.443 =   1  

O: 3.456/1.443 = 2.395

3. Multiply by a number to make the ratio close to an integer

P:  5 × 1         =  5

O: 5 × 2.395 = 11.97

3. Determine the empirical formula

Round off all numbers to the closest integer.  

P:   5

O: 12

The empirical formula is P₅O₁₂.