Question

The equilibrium constant at 298 K for a reaction $A+B\rightleftharpoons C+D$ is 100. If the initial concentration of all the four species were 1 M each, then equilibrium concentration of D (in mol $L^{-1}$) will be:

• A. 0.818
• B. 1.818
• C. 1.182
• D. 0.182

Answer 1

The correct option is B

1.818

$A+B\rightleftharpoons C+D$

initially 1 1 1 1 [D]eq = 1.818 M

Q =1

Q < keq

$\therefore$ Equilibrium is forward shifted.

$A+B\rightleftharpoons C+D$

Equilibrium: 1 - x 1 - x 1+x 1+x

$\frac{(1+x{)}^2}{(1-x{)}^2}={10}^2$
$\Rightarrow \frac{1+x}{1-x}=10$
$\Rightarrow 1+x=10-10x$
$\Rightarrow 11x=9$
$\therefore x=\frac{9}{11}=0.818$

So, equilibrium concentration of 'D' = 1.818 M.