Complete the following sentences by choosing the correct answer from the brackets:

(a) The metal to be refined is kept at the …………… during the process of electro-refining. [cathode / anode]

(b) Dilute HCl and dilute H₂SO₄ can be distinguished by adding …………… solution. [NaNO₃ / BaCl₂]

(c) Ammonia gas is collected by …………… displacement of air. [upward / downward]

(d) The gas formed when copper carbonate is heated is …………… [O₂ / CO₂]

(e) Excess ammonia reacts with chlorine to form …………… [nitrogen / nitrogen trichloride]

State the terms for the following:

(a) A substance which when dissolved in water forms hydronium ion as the only positive ion.

(b) A type of covalent bond in which electrons are shared equally between the combining atoms.

(c) The process by which a base metal is coated with another metal, either to protect the metal or to give it an attractive appearance.

(d) The type of reaction characteristic for alkanes.

(e) The substance which oxidises the other substance and itself gets reduced.

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.