Question

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%.
(i) Calculate the empirical formula of the minor product.
(ii) When 5.5 gm of the minor product is dissolved in 45 gm of benzene, the boiling point of the solution is 1.84C higher than that of pure benzene. Calculate the molar mass of the minor product and determine its molecular and structural formulae.

Answer 1

Empirical formula of minor product of nitration of nitrobenzene.

Element	Percentage	At.wt	Relative number	Ratio
C	42.86	12	$\frac{42.86}{12}=3.57$	$\frac{3.57}{1.19}=3.00$
H	2.40	1	$\frac{2.40}{1}=2.40$	$\frac{2.40}{1.19}=2.00$
N	16.67	14	$\frac{16.67}{14}=1.19$	$\frac{1.19}{1.19}=1.00$
O	38.07	16	$\frac{38.07}{16}=2.37$	$\frac{2.37}{1.19}=1.99=2.0$

Hence, the empirical formula of minor product $=C_3{H}_{2}N{O}_2$

Mw of minor product (m) $=\frac{1000\times K_b}{\Delta T_b}\times \frac{w}{W}$

$=\frac{1000\times 2.53}{1.84}\times \frac{5.5}{45}=168$

$\therefore n=\frac{Mw}{Wt.ofempiricalformula}$

$=\frac{168}{36+2+14+32}=2$

Hence, the molecular formula of the minor product is

$=2\times C_3{H}_{2}N{O}_2=C_6{H}_4{N}_2{O}_4$

Hence,according to above image minor product is m -Dinitrobenzene.