Question

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

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

Answer 1

The correct option is B 1.818

$A+B\rightleftharpoons C+D$
Initial Conc. 1 1 1 1
At Equilibrium $1-x1-x1+x1+x$

$K_{eq}=\frac{\left[C\right]\left[D\right]}{\left[A\right]\left[B\right]}=\frac{(1+x)(1+x)}{(1-x)(1-x)}={\left(\frac{1+x}{1-x}\right)}^2$

${\left(\frac{1+x}{1-x}\right)}^2=100\to \frac{1+x}{1-x}=10$

$\therefore x=0.818$

$\left[D\right]=1+x=1+0.818=1.818$