Question

The group reagent for group V radicals is

• A. $(N{H}_4{)}_{2}C{O}_3$
• B. $(N{H}_4{)}_{2}S{O}_4$
• C. $N{H}_{4}Cl$
• D. $(N{H}_4{)}_2{C}_2{O}_4$

Answer 1

The correct option is A $(N{H}_4{)}_{2}C{O}_3$

For the analysis of cations belonging to groups I-VI, the cations are precipitated from original solution by using the group reagents.
Group I reagent is dil.HCl.
Here, the group I cations like $P{b}^{2+}$ precipitate as chlorides.

If group-I is absent, add excess of water to the same test tube and warm the solution and pass $H_{2}S$ gas
for 1-2 minutes. Here, the group II cations like $P{b}^{2+}$, $C{u}^{2+},A{s}^{3+}$ precipitate as sulphides.

If group-II is absent, take original solution and add 2-3 drops of $conc.HN{O}_3$ and heat the solution for few minutes.
After cooling add a small amount of solid $N{H}_{4}Cl$ and an excess of $N{H}_{4}OH$ solution till it smells ammonia. Here, cations will precipitate as hydroxide i.e $Al(OH{)}_3,Fe(OH{)}_3$ etc.

If group-III is absent, pass $H_{2}S$ gas in the solution of group-III. Sulphides of group IV cations will get precipitated.

If group-IV is absent then take original solution and add a small amount of solid $N{H}_{4}Cl$ and an excess of $N{H}_{4}OH$ solution followed by solid ammonium carbonate $(N{H}_4{)}_{2}C{O}_3$. Group–V cations are precipitated as their carbonates.
Thus, $(N{H}_4{)}_{2}C{O}_3$ is the group V reagent.