(i) (a) Hydrogen gas will evolve with greater speed.
(b) Almost same amount of gas is evolved.
(c) If sodium hydroxide is taken, hydrogen gas will be evolved.
Zn + 2NaOH → Na2ZnO2 + H2
(ii) All metal carbonates and hydrogen carbonates react with acids to form a corresponding salt, carbon dioxide and water.
Metal carbonate + Acid → Salt + Carbon dioxide + Water
Metal hydrogencarbonate + Acid → Salt + Carbon dioxide + Water
For example, sodium carbonate reacts with dilute hydrochloric acid as follows:
Na2CO3 (s) + 2HCl → 2NaCl + H2O + CO2
Sodium hydrogen carbonate reacts with dilute hydrochloric acid as follows:
NaHCO3 (s) + HCl (aq) → NaCl (aq) + H2O + CO2