Question

Nitrobenzene is formed as the major product along with aminor product in the reaction of benzene with a hot mixtureof 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 $5.5g$ of the minor product is dissolved in $45g$ ofbenzene, the boiling point of the solution is $1,84^{\circ }C$ higherthan that of pure benzene. Calculate the molar mass of theminor product then determine its molecular and structuralformula. (Molal boiling point elevation constant of benzene is $2.53K.kgmo{l}^{-1})$.

Answer 1

(i) Empirical formula determination

Elements	C	H	N	O
Weight %	42.86	2.40	16.67	38.07
Moles	3.57	2.40	1.19	2.38
Simplest ratio	3	2	1	2

$\Rightarrow$ Empirical formula $=C_3{H}_{2}N{O}_2$
(ii) $\Delta T_b=1.84=2.53\times \frac{5.5}{M}\times \frac{1000}{45}$
$\Rightarrow M=168$
$\because$ Empirical formula weight $(84)$ is half of molar mass, molecular formula is $C_6{H}_4{N}_2{O}_4$ a dinitrobenzene :