Question

Name the acidic radicals that are detected when concentrated ${H_2}S{O_4}$ is used along with:Copper turnings.

Answer 1

An acidic radical can be identified on the basis of qualitative analysis. The qualitative analysis of inorganic compounds in the aqueous solution is being based upon on some factors that are as follows:
1.Physical test (Colour and smell).
2.Dry Heating test.
3.Identification of acidic radicals (anions) includes determination by wet tests.

Complete step by step answer:
As mentioned, we will discuss the qualitative analysis in detail.
First, we will heat the concentrated ${H_2}S{O_4}$with pinch of salt i.e. $NaN{O_3}$ and the reaction can be written as follows:
$NaN{O_3} + {H_2}S{O_4} \to NaHS{O_4} + HN{O_3}$
$4HN{O_3} \to 4N{O_2} + {O_2} + 2{H_2}O$
In this reaction evolution of $N{O_2}$ gas is confirmed as brown colour fumes are attained.
Now, further we will heat the small quantity of given salt with the copper turnings and conc. ${H_2}S{O_4}$. The reaction is as follows:
$2NaN{O_3} + 4{H_2}S{O_4} + 3Cu \to 3CuS{O_4} + N{a_2}S{O_4} + 4{H_2}O + 2NO$
Here, copper sulphate solution is formed, i.e. deep blue colour
$2NO + {O_2} \to 2N{O_2}$
So, with the help of preliminary test i.e. evolution of brown colour fumes and the confirmatory test which indicates the formation of copper sulphate solution identifies the presence of nitrate ions when treated with the copper turnings.
In the last, we can conclude that nitrate ions are the acidic radicals being detected.

Note: There are some other tests performed for identification of ions. The insoluble salts are excluded to confirm the presence of ions. The qualitative analysis is based on two principles as follows:
1.Solubility product
2.Common ion effect
Solubility of salt helps to identify the nature of ions present in the solution like anions or cations. If on being soluble salt the solution turns to be acidic or basic then it is being hydrolysed in water.