Question

How many grams of H2O will be formed when 32.0 g H2 is mixed with 76.0 g of O2 and allowed to react to form water?

Answer 1

2 H₂ + O₂ -----> 2 H₂O

Number of moles of H2 = 32.0 g / 2.016 g/mol = 15.9 mol

Number of moles of O2 = 76.0 g / 32.0 g/mol = 2.38 mol

From the balanced equation we can say that

2 mole of H2 requires 1 mole of O2 so

15.9 mole of H2 will require

= 15.9 mole of H2 *(1 mole of O2 / 2 mole of H2)

= 7.95 mole of O2

But we have 2.38 mole of O2 which is in short so o2 is limiting reactant

From the balanced equation we can say that

1 mole of O2 produces 2 mole of H2O so

2.38 mole of O2 will produce

= 2.38 mole of O2 *(2 mole of H2O / 1 mole of O2)

= 4.76 mole of H2O

mass of 1 mole of H2O = 18.016 g so

the mass of 4.76 mole of H2O = 85.8 g

Therefore, the mass of H2O produced would be 85.8 g