Properties and Preparation of Ammonia

Steps:

• Identify ammonia's physical state and odor: colorless gas with pungent smell.
• Check its reaction with litmus: basic, so turns damp red litmus blue.
• Recall lab preparation: ammonia forms from reduction of nitrates using aluminium and alkali.
• Note industrial process: Haber-Bosch uses iron catalyst.

Why C is correct:

• Ammonia is liberated when potassium nitrate (a nitrate salt) is reduced by aluminium in aqueous sodium hydroxide, per the reaction 3NO3^- + 8Al + 5OH^- + 18H2O → 3NH3 + 8Al(OH)4^-.

Why the others are wrong:

• A: Ammonia has a strong pungent odor, not odorless.
• B: As a base, ammonia turns damp red litmus blue, not blue litmus red.
• D: Industrial ammonia synthesis (Haber process) uses iron oxide catalyst, not vanadium(V) oxide.

Final answer: C