Question

In a system: $A ( s ) \rightleftharpoons 2 B ( g )+3 C ( g )$. If the concentration of $C$ at equilibrium is increased by a factor 2 , it will cause the equilibrium concentration of $B$ to change to:

• A. Two times of its original value
• B. One half of its original value
• C. $2 \sqrt{2}$ times of its original value
• D. $\frac{1}{2 \sqrt{2}}$ times of its original value

Answer 1

Answer: (D)

For $A ( s ) \rightleftharpoons 2 B ( g )+3 C ( g )$

$\therefore K_{c}=[C]^{3}[B]^{2}$ ; if $[C]$ becomes twice,

Then let conc. of $B$ becomes $B ^{\prime}$, then

$K _{ c }=[2 C ]^{3}\left[ B ^{\prime}\right]^{2} $

or ${[ C ]^{3} \cdot[ B ]^{2}=[2 C ]^{3} \cdot\left[ B ^{\prime}\right]^{2}}$

$\therefore \frac{\left[B^{\prime}\right]}{[B]}=\frac{1}{8}=\frac{1}{2 \sqrt{2}}$