chemistry stoichiometry question

Question

If 0.375 moles of hydrogen are made in the reaction of zinc with hydrochloric acid, how many moles of zinc were used?

Answer 1

To determine the amount of products produced, generate a balanced equation and proceed by using the mole ratios in the equation.

Zn + HCl --> ZnCl₂ + H₂

2Zn + 2HCl --> 2ZnCl₂ + H₂ (balancing Chlorine also balances hydrogen, note two zinc atoms are needed for this)

Thus we see that 2 moles of zinc produce 1 mole of hydrogen. Use the law of proportions and

1 mole of hydrogen is produced from 2 moles of zinc in this reaction thus

0.375 moles of hydrogen are produced from 2 times 0.375 = 0.750 moles of zinc