In the given equation

Zn + Pb²⁺ ⟶ Zn²⁺ + Pb

(a) …………… undergoes oxidation.

(b) …………… undergoes reduction.

Justify the following statements:

(a) As one moves down a group, the reducing property of elements increases.

(b) Aluminium oxide cannot be reduced by carbon monoxide.

Harsh performed the following experiments in the laboratory. State one significant observation made by Harsh when:

(a) he added concentrated sulphuric acid to blue vitriol.

(b) he passed ammonia gas over heated PbO.

(c) sodium hydroxide solution was added to CuSO₄ solution by him.

Choose the letters L, M, N, O & P to match the description (a) to (c) given below:

[L – Ammonia, M – Nitrogen, N – Hydrogen sulphide, O – Hydrogen chloride gas, P – Nitrogen dioxide]

(a) When this gas comes in contact with ammonia dense white fumes are seen.

(b) The gas that turns moist lead acetate paper silvery black.

(c) The gas produced on heating lead nitrate.