Question

What is a group reagent? Name the group reagents for second, third and fourth groups of mixture analysis.

Answer 1

Hint : The anionic part of the salt is known as acid radical while the cationic part of salt is known as basic radical. The group reagents are the combination of reagents which are used to identify the basic radical (cation) in the given salt. There are different sets of reagents required to identify the basic radicals of different groups which we will see in detail.

Complete Step By Step Answer:
The anionic part of the salt is known as acid radical while the cationic part of salt is known as basic radical. For the salt analysis all the basic radicals are divided into different groups.
Now, we know that the group reagents are the combination of reagents which are used to identify the basic radical (cation) in the given salt. There are different sets of reagents required to identify the basic radicals of different groups.
For different groups of mixture analysis reagents are:
Second group- Second group consists of cations like $P{b^{2 + }},C{u^{2 + }},A{s^{2 + }}$ and the group reagent is Hydrogen Sulphide $({H_2}S)$ in presence of dilute HCl.
Third group- Third group cations are $F{e^{3 + }},A{l^{3 + }}$ and the group reagent is $N{H_4}OH\;$ in presence of Ammonium chloride $(N{H_4}Cl)$ .
Fourth group- Fourth group cations are $N{i^{2 + }},C{o^2}^ + ,M{n^{2 + }},Z{n^{2 + }}$ and the group reagent is Hydrogen Sulphide $({H_2}S)$ in presence of $N{H_4}OH\;$ .

Note :
These acidic radicals (anions) are also classified into three groups. The first group anions are $C{O_3}^{2 - },{S^{2 - }},S{O_3}^{2 - }$ and $N{O_2}^-$ , the reagent is dilute HCl. The second group anions are $C{l^-},B{r^-},{I^-},{C_2}{O_4}^{2 - }$ and the group reagent is concentrated HCl. The group third has interfering anions like sulphate ion and phosphate ion which have independent tests for analysis.