Which of the following is used in rocket fuels?

1. Analyze the question You are asked which of the listed acids is used in rocket fuels, that is, as an oxidizer or propellant component.

2. Explain the concept A rocket needs a fuel and an oxidizer that supplies oxygen for combustion, since there is no air in space. Nitric acid is a strong oxidizing agent. Its oxidizing power is why it is used in propellants. Mixtures such as red fuming nitric acid (RFNA) have been paired with fuels like hydrazine or kerosene-type fuels in liquid-propellant rockets.

3. Go through the options

• A. HNO₃ (nitric acid): A powerful oxidizer. Used as an oxidizer in liquid rocket propellants. ✔
• B. CH₃COOH (ethanoic acid): A weak organic acid, used in vinegar and for making esters and plastics. It is not a rocket propellant.
• C. H₂SO₄ (sulphuric acid): Used for fertilizers, car batteries and the chemical industry. It is a dehydrating agent, not a propellant.
• D. HCl (hydrochloric acid): Used for pickling metals and cleaning. It is not used as rocket fuel.

4. Answer The correct option is A. HNO₃.

5. Tip For "uses of acids" questions, remember these pairings:

• HNO₃ → oxidizer in explosives and rocket fuel, and fertilizers (ammonium nitrate)
• H₂SO₄ → car batteries, fertilizers, detergents
• HCl → metal cleaning, stomach acid
• CH₃COOH → vinegar

Remember "Nitric = Nitro = explosive or propellant".