Assertion (A): Reduction is defined as the process of removal of oxygen from a substance or the addition of hydrogen to a substance.

Reason (R): Hydrogen is a reducing as well as an oxidising agent.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Choose terms from the options given in brackets to complete these sentences.

(a) When CuO reacts with hydrogen, …………… is reduced to …………… and …………… is oxidized to …………… . (CuO, H₂, Cu, H₂O)

(b) Hydrogen is …………… soluble in water. (sparingly, highly, moderately)

(c) Metals like ……………, …………… and …………… give H₂ with steam. (iron, magnesium, aluminium, sodium, calcium)

(d) Sodium …………… reacts smoothly with cold water. (metal, amalgam, in the molten state)

(e) A metal …………… hydrogen in the activity series gives hydrogen with …………… acid or …………… acid. (above, below, dilute hydrochloric, concentrated hydrochloric, dilute sulphuric).

Correct the following statements:

(a) Hydrogen is separated from CO by passing the mixture through caustic potash solution.

(b) All metals react with acids to give hydrogen.

(c) Hydrogen is dried by passing it through conc. H₂SO₄.

(d) Very dilute nitric acid reacts with iron to produce hydrogen.

(e) Conc. H₂SO₄ reacts with zinc to liberate hydrogen.

Divide the following redox reactions into oxidation and reduction half reactions.

(i) Zn + Pb²⁺ ⟶ Zn²⁺ + Pb

(ii) Zn + Cu²⁺ ⟶ Zn²⁺ + Cu

(iii) Cl₂ + 2Br^- ⟶ Br₂ + 2Cl^-