Attempt either (a) or (b) : (a) Give reasons : (i) For dilution of an acid, acid is added into water and not…
Attempt either (a) or (b) :
(a) Give reasons :
(i) For dilution of an acid, acid is added into water and not water into acid.
(ii) Dry HCl gas does not turn blue litmus red whereas dilute hydrochloric acid does.
(iii) Blue colour of Copper(II) sulphate crystals turns white on heating.
Solution
(a) (i) When acid is added to water, it does not cause excessive local
heating/ does not splash out and cause burns.
(ii) Because dry HCl does not ionize/produce H+ ions whereas in
dilute HCl, H+ ions are present.
(iii) Because of loss of 5 molecules of water of crystallisation.
OR
electricity
(b) (i) 2NaCl(aq) + 2H2 O(l) → 2NaOH(aq) + H2 (g) + Cl2 (g)
(ii) NaCl + H2 O + NH3 + CO2 → NaHCO3 + NH4 Cl
373K
(iii) CaSO4 .2H2 O → CaSO4 . 2 H2 O + 1 2 H2 O
(Deduct ½ mark if no/ incorrect balancing in each case)