Explanation:
A.
Mass of evaporation dish + solution of KCl = mass of dish + mass of solution of KCl
61.945 = 54.73 + mass of KCl solution
= 7.215 g
Mass of evaporation dish + dry KCl = mass of dish + mass of dry KCl
55.428 = 54.73 + mass of dry KCl
= 0.698 g.
% Mass of KCl = mass of dry KCl/mass of KCl solution * 100
= 0.698/7.215 * 100
= 9.67%
B.
At 10%, mass = 0.7215 g
Change in error = 0.7215 - 0.698
= 0.0235 g
% error = change in error/actual mass at 10% * 100
= 0.0235/0.7215 * 100
= 3.26 %
C.
In evaporation, KCl does not decompose on heating. In filtration, there needs to be a heterogeneous solution(particles or suspension of KCl present) and it is not suitable for soluble salts while recrystallisation is mainly a purification process for solution and KCl is equally soluble in cold and hot water.