Inquiries on the separation of Group III Cations?

Question

in the separation of zinc and iron:
add 5drops of 5% thioacetamide and heat the mixture in a hot water bath. then, add 6 M HCl to the precipitate until it dissolves. after that, heat the solution, then neutralize it with 6 M NH3 (ammonia). also, add 10 drops of 1 M HCl before adding 5 drops of 0.1 M K4Fe(CN)6.

why do we need to add 10 drops of 1 M HCl when we already added 6 M HCl and neutralized it?

thanks! :)

Answer 1

The small amt of HCl is required to remove any NH3 which may have escaped neutralisation as NH4+.

Answer 2

given which you reported chromium ion, meaning the chromium atom is dissolved into OH and H ions. Ammonium Chloride is comfortably dissociated into NH3 and HCl. HCl can dissociate into its respective ions H+ and Cl-. The Cl- will bond with the Cr3+ to grant u CrCl3, nonetheless this purely isn't the main significant product shaped.