During the estimnation of nitrogen by Kjeldhal's method, coper sulphate is added to sulphuric acid.why?

During the estimation of nitrogen by Kjeldahl's method, copper sulphate is added to :

During the nitration of benzene, nitric acid is used in the presence of conc. Sulphuric acid. The sulphuric acid is used :

During nitrogen estimation present in an organic compound by Kjeldahl.s method, the ammonia evolved from 0.5 g of the compound in Kjeldahl.s estimation of nitrogen neutralised 10 ml of 1 M H_(2)SO_(4) . Find the percentage of nitrogen in the compound.

The ammonia evolved from 0.21 g of an organic compound by Kjeldahl method neutralised 15 ml of N/20 sulphuric acid solution. Calculate the percentage of nitrogen.

For the estimation of nitrogen 1.4g of an organic compound was digested by Kjeldahl method and the evaloed ammonia was absorbed in 60mL of (M)/(10) sulphuric acid. The unreacted acid required 20mL of (M)/(10) sodium hydroxide for complete neutralisation . The percentage of nitrogen in the compound is

Name the compound formed where ethanol is heated is excess of concentrated sulphuric acid at 443 K. Also write the chemical equation of the reaction stating the role of concentrated sulphuric acid in it. What would happen if hydrogen is added to the product of this reaction in the presence of a catalyst such as potassium or nickel?

In an estimation of sulphur by Carius method, 0.160g of the substance gave 0.466g of barium sulphate. The percentage of sulphur in the compound is [At mass of Ba=137 , S=32 , O=16 ] :

Nitrobenzene is formed as the major product along with a minor product in the reaction of benzene with a hot mixture of nitric acid and sulphuric acid. The minor product consists of carbon 42.86% , hydrogen 2.40% , nitrogen 16.67% and oxygen 38.07% . a. Calculate the empirical formula of the minor product.