Question -
Answer -
(i) iron with steam
(ii) calcium and potassium with water
Answer
(i) Iron reacts with steam to form a magnetic oxide of Fe with the liberation of H2.
3Fe(s) + 4H2O(g) → Fe3O4(s)+ 4H2(g)
(ii) Calcium reacts with water to form calcium hydroxide and hydrogen.
Ca(s) + 2H2O(I) → Ca(OH)2(aq)+ H2(g)
Potassium reacts with cold water violently immediately with evolution of H2 which catches fire.
2K(s) + 2H2O(I) → 2KOH(aq) + 2H2(g)