How do we differentiate between Fe^3+ and Cr^3+ in group III?

a. by taking excess of NH base 4OH solution

b. by increasing NH base 4^+ ion concentration

c. by decreasing OH^- ion concentration

d. both (b) and (c)

(b) When we add NH base 4CI, it suppresses the ionization of NH base 4OH and prevents the precipitation of higher group hydroxide in gp (III).

NOTE : Further ferric chloride and chromium chloride form different colour precipitates with NH base 4OH.

FeCI base 3 + 3NH base 4OH ? Fe(OH) base 3 ? + 3NH base 4CI

Reddish brown

CrCI base 3 + 3NH base 4OH ? Cr(OH) base 3 + 3NH base 4CI