Reactants' sources and Haber process catalyst

Steps:

• Identify Haber process reaction: N₂ + 3H₂ ⇌ 2NH₃, requiring a catalyst.
• Determine nitrogen source: obtained from air via fractional distillation to separate it from oxygen.
• Determine hydrogen source: produced by steam reforming of natural gas, not distillation.
• Recall catalyst: finely divided iron promotes the reaction.

Why D is correct:

• Nitrogen is isolated by fractional distillation of liquid air, and iron acts as the catalyst per industrial chemistry standards.

Why the others are wrong:

• A: Omits reactant; nickel is not the catalyst.
• B: Hydrogen is not from distillation; iron is correct catalyst but wrong pairing.
• C: Nitrogen is correct but nickel is incorrect catalyst.

Final answer: D