Final answer:
To completely react with 4.0 moles of lead, you would need 8.0 moles of hydrochloric acid.
Step-by-step explanation:
When lead reacts with hydrochloric acid, it forms lead (II) chloride and hydrogen gas. The balanced chemical equation for this reaction is:
From the balanced equation, we can see that 2 moles of lead react with 4 moles of hydrochloric acid to produce 2 moles of lead (II) chloride and 1 mole of hydrogen gas. Therefore, to completely react with 4.0 moles of lead, we would need 8.0 moles of hydrochloric acid.