The critical temperature of a gas is the temperature: MCQ with Answer and Explanation

Explanation:
Cu + 4HNO₃ (conc.) → Cu(NO₃)₂ + 2NO₂ + 2H₂O. Dilute HNO₃ gives NO instead of NO₂. Copper does not produce H₂ with HNO₃ because HNO₃ is an oxidizing acid.

Explanation:
Reverse osmosis (RO) uses pressure to force water through a membrane that blocks dissolved salts and impurities. Distillation uses boiling/condensation. Chlorination and ozonation are disinfection methods, not for desalination.

Explanation:
Physical changes alter the form, state, or appearance without changing chemical identity. They are usually easily reversible (e.g., freezing/melting). Chemical changes produce new substances and are often irreversible (e.g., burning). Physical: crushing, dissolving, boiling. Chemical: rusting, cooking, digestion.