1. Balanced Chemical Equation:

The reaction between copper oxide (CuO) and hydrogen gas (H₂) is:

CuO + H₂ → Cu + H₂O

2. Mole Ratio:

From the balanced equation, we see that 1 mole of H₂ reacts with 1 mole of CuO.

3. Calculation:

Since we have 5.51 moles of CuO, we need an equal amount of H₂ to react completely.

Therefore, we need 5.51 moles of H₂.

4. Convert Moles to Grams:

To convert moles of H₂ to grams, we use the molar mass of H₂ (2.016 g/mol).

Mass of H₂ = (5.51 moles H₂) * (2.016 g/mol) = 11.1 g H₂

Answer: You need 11.1 grams of H₂ to reduce 5.51 moles of CuO.