Turmeric stain on a white cloth turns reddish-brown when rubbed with soap solution because soap is: MCQ with Answer and Explanation

Explanation:
Magnesium oxide (MgO) is a basic oxide because it reacts with acids to form salt and water, e.g., MgO + 2HCl → MgCl₂ + H₂O. However, Reason is false: Metals generally form basic oxides, not acidic oxides. Non-metals form acidic oxides (e.g., SO₂, CO₂). Some metals like Al, Zn form amphoteric oxides. So A is true, R false. Exam tip: Metal oxides are usually basic; non-metal oxides are acidic.

Explanation:
Physical changes affect form or state but not chemical composition. They can be reversible (melting/freezing). No new substances form. They may be endothermic or exothermic. Example: dissolving salt in water – salt is still NaCl.

Explanation:
Endothermic reactions absorb heat from the surroundings. The decomposition of calcium carbonate (CaCO₃ → CaO + CO₂) requires continuous heating to proceed. Burning of gas, respiration, and the reaction of sodium with water are all exothermic reactions that release significant amounts of heat energy to the surroundings.