Question

A mixture of ${H_{2}}$,${N_{2}}$ and ${O_{2}}$ occupying 100ml, underwent reaction so as to form a ${H_{2}}{O_{2}}$ (l) and ${N_{2}}{H_{2}}$ as the only products, causing the volume to contract by 60ml. The remaining mixture was passed through pyrogallol causing a contraction of 10ml. To the remaining mixture, excess ${H_{2}}$ was added and the above reaction was repeated, causing a reduction in the volume of 10ml. Identify the composition of the initial mixture in ml (No other products are formed).
(a) ${N_{2}}$=30ml, ${H_{2}}$=40ml
(b) ${N_{2}}$=32ml, ${H_{2}}$=30ml
(c) ${N_{2}}$=36ml, ${H_{2}}$=46ml
(d) ${N_{2}}$=29ml, ${H_{2}}$=31ml

Answer 1

Hint: Pyrogallol is an organic compound used to check and quantify the amount of oxygen in chemical mixtures. The alkali solutions of Pyrogallol are quite efficient in absorbing oxygen and used in determining the content of oxygen in gaseous mixtures.

Complete step by step answer:
As per given in the question, we will first mention the reactions that are taking place.
$
H_{2}+O_{2}\rightarrow H_{2}O_{2}…(1)
$
$
H_{2}+N_{2}\rightarrow N_{2}H_{2}…(2)
$
Now, in equation (1), if x amount of hydrogen reacts with oxygen to form ${H_{2}}{O_{2}}$, then the volume of oxygen will also be x.
Similarly, in equation (2), if y amount of hydrogen reacts with oxygen to form ${N_{2}}{H_{2}}$, then the volume of oxygen will also be y.
According to this, the total volume of hydrogen, oxygen, and nitrogen will be
$H_{2} = x + y$
$N_{2} = y$
$O_{2} = x$
Now, we know that after reacting equation (1) with pyrogallol i.e., ${C_{6}}{H_{3}}{O_{3}}$, 10ml of oxygen is consumed. So the volume of oxygen will become
$O_{2} = x + 10$

Now, on reacting equation (2) with excess H_{2}, 10ml of nitrogen is consumed. So, volume of nitrogen will become
$N_{2}= y + 10$
Initially, we were given 60ml volume.
So, $2x + y = 60…(3)$
Now, total consumed volume will be shown as
$2x + 2y = 80…(4)$
Now, by using equations (3) and (4), we get the values of x and y as
 x = 20ml
Y = 20ml
Since, $N_{2}= y + 10$
$N_{2}= 20 + 10 = 30ml$
And $H_{2} = x + y$
$H_{2}= 20 + 20 = 40ml$

Therefore, the answer to the question is (A) ${N_{2}}$=30ml, ${H_{2}}$=40ml

Note: Pyrogallol is also known as pyrogallic acid or 1,2,3-trihydroxy benzene. It is an organic compound which belongs to the phenol family. It is also used as a photographic film developer and in the preparation of various other chemicals.