The reaction of sodium peroxide and water produces sodium hydroxide and oxygen gas. The following balanced chemical equation represents the reaction.

2 Na^2O^2 (s) + 2 H2O (l) → 4 NaOH (s) + O^2 (g)

If 15.7 moles of sodium hydroxide are produced, how many moles of O2 will be made?

3.925 mol.

Explanation:

From the balanced equation:

2 Na₂O₂ (s) + 2 H₂O (l) → 4 NaOH (s) + O₂ (g),

It is clear that 2 moles of Na₂O₂ react with 2 moles of H₂O to produce 4 moles of NaOH and 1 mole of O₂.

Using cross multiplication:

4 moles of NaOH produced with → 1 mole of O₂.

15.7 moles of NaOH produced with →? mole of O₂.

∴ The no. of moles of O₂ made = (1 mole) (15.7 mole) / (4 mole) = 3.925 mol.