Which acid is called the 'King of Chemicals'? MCQ with Answer and Explanation

Explanation:
Hydrogen has a higher calorific value than CNG, making it a better fuel in terms of energy output per unit mass. However, R states it is explosive and hard to store, which is a disadvantage, not the reason it is a better fuel. Thus, both are true, but R does not explain A.

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.

Explanation:
Detergents do not form scum with Ca²⁺/Mg²⁺, so they clean effectively in hard water. Soaps form insoluble precipitates. Biodegradability varies; some detergents are non-biodegradable.