Question

In Kjeldahl's method $CuS{O_4}$ acts as:
A.Oxidizing agent
B.Reducing agent
C.Hydrolysing agent
D.Catalytic agent

Answer 1

Kjeldahl’s method is one of the important methods for the Estimation of elements in organic compounds. We should focus on the principle and the procedure of Kjeldahl’s method. With the help of the reactions used in Kjeldahl’s method, we can give a conclusion about $CuS{O_4}$.

Complete answer:
First, we will understand the basic principle of Kjeldahl's method. With help of principle, we can understand the basics of Kjeldahl's method.
Principle: When a nitrogenous organic substance is heated with concentrated ${H_2}S{O_4}$, their nitrogen is completely converted to ammonium sulphate. The reaction mixture when heated with caustic alkali evolves ammonia which is passed in a known volume of standard acid solution.
Now we know the basic principle of Kjeldahl’s method. We can understand the method with the help of reactions given below.
$N\xrightarrow{{{H_2}S{O_4}}}{\left( {N{H_4}} \right)_2}S{O_4}$
${\left( {N{H_4}} \right)_2}S{O_4} + 2NaOH\xrightarrow{{}}N{a_2}S{O_4} + 2N{H_3} + 2{H_2}O$
$2N{H_3} + {H_2}S{O_4}\xrightarrow{{}}{\left( {N{H_4}} \right)_2}S{O_4}$
From the above reactions, we can understand the procedure that some amount of organic substance is taken in a long-necked round bottom flask with concentrated ${H_2}S{O_4}$. Some amount of ${K_2}S{O_4}$ and some crystals of $CuS{O_4}$ copper sulphate is added.
The function ${K_2}S{O_4}$ is to raise the boiling point of ${H_2}S{O_4}$. So that it facilitates the completion of the reaction that is the conversion of the nitrogenous compound into ${\left( {N{H_4}} \right)_2}S{O_4}$. Here, the copper sulphate $CuS{O_4}$ acts as a catalyst. So, we can conclude that copper sulphate acts as a catalytic agent.

Therefore, the correct option is (D).

Note:
Kjeldahl’s method is used for the estimation of nitrogen in food products and fertilizers. The method is not an accurate one, only an approximate percentage of nitrogen can be calculated.This method is easy as compared to Duma’s method which is also used for estimation of nitrogen.