Question

Ammonia gas at $76cmHg$ pressure was connected to a manometer. After sparking in the flask, ammonia is partially dissociated as follows:
$2N{H}_3\left(g\right)\rightleftharpoons N_2\left(g\right)+3H_2\left(g\right)$
the level in the mercury column of the manometer was found to show the difference of $18cm$. What is the partial pressure of $H_2\left(g\right)$ at equilibrium?

• A. $18cmHg$
• B. $9cmHg$
• C. $27cmHg$
• D. $24cmHg$

Answer 1

Answer: (C)

$27cmHg$

$2H_3\left(g\right)\rightleftharpoons N_2\left(g\right)+3H_2\left(g\right)$

Initially: $7600$

At time t: $76-2xx3x$
Total pressure after dissociation $=76-2x+x+3x=76+2x$
$\therefore$ Increase in pressure $=2x=18$
$x=9cm$
Partial pressure of $H_2=3x=27cm$.