How many moles of hydrogen gas would be needed to react with excess carbon dioxide to produce 42.1 moles of water vapor?

84.2 mol hydrogen gas (H₂) woiuld be needed to react with excess carbon dioxide to produce 42.1 moles of water vapor.

Explanation:

1) Word equation:

2) Molecular equation:

3) Balanced molecular equation:

4) Stoichiometric mole ratios:

5) Set a proportion with the stoichiometric mole ratios, the moles of water vapor produced and the unknown:

     ⇒ x = 42.1 mol H₂O × 4 mol H₂ / 2 mol H₂O = 84.2 mol H₂ ← answer

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