Question

If 5 grams of hydrogen reacted with 40 games of oxygen to form water, how much of water would be formed?

Answer 1

2H₂ + O₂ = 2H₂O

n(H₂)=m(H₂)/M(H₂)
n(H₂)=5g/2.0g/mol=2.5 mol

n(O₂)=m(O₂)/M(O₂)
n(O₂)=40g/32.0g/mol=1.25 mol

H₂ : O₂ = 2 : 1

2.5 : 1.25 = 2 : 1

n(H₂O)=n(H₂)=2n(O₂)=2.5 mol

m(H₂O)=n(H₂O)M(H₂O)

m(H₂O)=2.5mol*18.0g/mol=45.0 g