Question

A closed flask contains $N{H}_3$ gas at 76 cm of Hg pressure. Now a spark is created due to which, ammonia gas partially dissociates into $N_2$ and $H_2$. The mixture is then allowed to attain same intial temperature, the total pressure of the mixture was found to be 82 cm of Hg. Calculate the partial pressure of hydrogen ( in cm of Hg) in the final mixture.

Answer 1

Let the partial pressure of NItrogen gas be x cm of Hg
Reaction: $2N{H}_3\left(g\right)\rightleftharpoons N_2\left(g\right)+3H_2$
Before sparkling
pressure: 76 0 0
After sparkling, when equilibrium is reached,
Pressure: 76-2x x 3x
So, final pressure = $76-2x+x+3x$ = $76+2x$
Given, Final pressure = 82 cm of Hg
Equating, 82 = $76+2x$
We get, x = 3 cm of Hg
Partial pressure of Hydrogen = 9 cm of Hg