Nitrogen, a component of air is used for

Analyze the question: The question asks which of the options is a use of nitrogen, a component of air (about 78% by volume).

Concept: Nitrogen is fairly unreactive, but it can be converted into useful compounds and has several direct uses:

• Haber process: N₂ + 3H₂ ⇌ 2NH₃ (ammonia, used for fertilizers)
• Ostwald process: Ammonia is oxidised to make nitric acid (HNO₃)
• Liquid nitrogen is used as a refrigerant (a cooling agent)
• It provides an inert atmosphere for food packaging

Evaluate each option:

• A. Production of cooling agent: Liquid nitrogen is indeed used as a coolant, but it is used as a cooling agent rather than being used in its "production." The wording is awkward, which is why this is a distractor.
• B. Production of margarine: Margarine is made by hydrogenating vegetable oils with hydrogen gas and a nickel catalyst, so nitrogen is not the reagent. Wrong.
• C. Production of HNO₃: Nitrogen is converted to ammonia (Haber process), and then ammonia is oxidised to NO, then NO₂, which is absorbed in water to give nitric acid (Ostwald process). • 4NH₃ + 5O₂ → 4NO + 6H₂O (Pt catalyst) • 2NO + O₂ → 2NO₂ • 3NO₂ + H₂O → 2HNO₃ + NO

This is the standard textbook use of nitrogen.

• D. Manufacturing of oil: Nitrogen has no role here. Wrong.

Exam tip: Remember the chain N₂ → NH₃ → HNO₃ → fertilizers/explosives. Also remember that margarine goes with hydrogen and a nickel catalyst. JAMB often tests this contrast.