Question

Select a reagent used in Group III that will separate each of the following pairs:

(a) CoS , ZnS

(b) Fe³⁺, Al³⁺

(c) Zn(NH₃)_{4^{2+ ,}} CrO₄²

(d) Al³⁺ , Zn²⁺

(e) Mn²⁺ , Mg²⁺

Answer 1

Solution:

From quantitaive analysis the reagents used in the separation of listed Group III molecules are given below,

(a) CoS, ZnS are separated using Nitric acid (HNO₃) as it helps in precipating out Co²⁺and Zn²⁺ elements separately.

(b) Fe³⁺, Al³⁺ these are separated by adding base molecule NaOH where Al³⁺ will separated in the form of solution while Fe3+ gets settles down as precipitate.

(c) Zn(NH₃)₄²⁺, CrO₄^2- are separted using NaOCl solution where Zn is precipated and Cr element is separated as aqueous solution

(d) Al³⁺,Zn²⁺ a base solution of H₂S is added where Al is separate as aqueous hydroxide solution and Zn is precipitated out as ZnS.

(e) Mn²⁺,Mg²⁺ a base solution of H₂S is added where Mg is separate as aqueous hydroxide solution and Mn is precipitated out as sulfides.