Question

Total number of moles for the reaction $2HI$ $\rightleftharpoons$ $H_2+I_2$, if $\alpha$ is degree of dissociation is :

• A. $2$
• B. $2-\alpha$
• C. $1$
• D. $1-\alpha$

Answer 1

Answer: (A)

$2$

	$HI$	$\rightleftharpoons$ $H_2$ +	$I_2$
Initial moles	2	0	0
Change	$-\alpha$	$\frac{\alpha }{2}$	$\frac{\alpha }{2}$
moles at equilibrium	$2-\alpha$	$\frac{\alpha }{2}$	$\frac{\alpha }{2}$

The reaction is $2HI\rightleftharpoons H_2+I_2$.

$\alpha$ is the degree of dissociation.

Total number of moles $=2-\alpha +\frac{\alpha }{2}+\frac{\alpha }{2}=2$.