Answer to Question #249691 in General Chemistry for Soyeon

Question

A 50.00 g sample of a compound was analyzed and found to contain 21.85 g of

phosphorus and 28.15 g oxygen. What is the empirical formula for this compound?

Answer 1

Mass of phosphorus (P)= 21.85g

Mass of oxygen (O)= 28.15g

a). First we convert the mass of phosphorus and oxygen to moles;

The atomic mass of phosphorus is 30.97g

Therefore converting to that moles will be;

21.85g P × 1 mol P/30.97g P = 0.7055 mol P

For oxygen the atomic mass is 16.00g

Therefore;

28.15g O × 1 mol O/16.00g O = 1.759 mol O

b). Divide both moles by the smallest of the results

P: 0.7055 mol/0.7055 = 1

O: 1.759 mol/0.7055 =2.5

The non-whole number empirical formula is P₁O_2.5

c). We then multiply each of the moles by the smallest whole number that will convert each into a whole number

P:O =2(1:2.5)=2:5

The empirical formula of the compound is P₂O₅