Question

The ratio of the number of moles of hydrogen atoms required to get one mole of azobenzene and one mole of hydrazobenzene is :

• A. 4 : 5
• B. 5 : 4
• C. 1 : 1
• D. 2 : 3

Answer 1

Answer: (A)

4 : 5

When nitrobenzene is reduced in an alkaline medium, nitrosobenzene and phenylhydroxylamine are obtained. These intermediates react to form azoxybenzene.
Azoxybenzene on further reduction form azobenzene and hydrazobenzene.
Reduction of nitrobenzene to nitrosobenzene requires 2 H.
Reduction of nitrobenzene to phenylhydroxylamine requires 4 H.
Reduction of azoxybenzene to azobenzene requires 2 H.
Number of H involved in the conversion of nitrobenzene to azobenzene are 8
Reducttion of azobenzene to hydrazobenzene requires 2 H.
Number of H involved in the conversion of nitrobenzene to hydrazobenzene are 10
Thus the ratio of the number of H involved in the conversion of nitrobenzene to azobenzene and to hydrazobenzene is 8:10 or 4:5