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^-

Select the odd one out and justify your answer.

(a) Zn, Fe, Mg and Na

(b) SO₂, H₂S, NH₃ and CO₂

(c) Fe, Zn, Cu and Mg

(d) Fe, Pb, Al and Zn

Give reasons

(a) Hydrogen is collected by the downward displacement of water and not of air, even though it is lighter than air.

(b) A candle brought near the mouth of a jar containing hydrogen gas starts burning but is extinguished when pushed inside the jar.

(c) Apparatus for laboratory preparation of hydrogen should be airtight and away from a naked flame.