CBSE Class 10 Science 2020 · Paper 31/2/2 · Question 26(a)

(a) (i) ${\text{Al}}_2{\text{O}}_3+6\text{HCl}⟶2{\text{AlCl}}_3+3{\text{H}}_2\text{O}$ (ii) ${\text{K}}_2\text{O}+{\text{H}}_2\text{O}⟶2\text{KOH}$ (iii) $3\text{Fe}+4{\text{H}}_2\text{O}⟶{\text{Fe}}_3{\text{O}}_4+4{\text{H}}_2$ (iron reacts with steam) (b) X is more reactive than iron and, being a metal other than zinc, lies above zinc in the textbook activity series, so it is more reactive than zinc, copper and silver and displaces each of them from its salt solution. With copper sulphate the blue colour fades and a reddish-brown coating of copper forms on X; with zinc sulphate a grey coating of zinc forms on X; with silver nitrate a shiny greyish-white coating of silver forms on X. Increasing order of reactivity: $\text{Ag}<\text{Cu}<\text{Zn}<\text{X}$.