Question

For the reaction $3A\left(g\right)+B\left(g\right)\rightleftharpoons 2C\left(g\right)$, at the given temperature, $K_c=9.0$. What must be the volume of the flask, if a mixture of $2.0$ mol each of $A,B$ and $C$ exist in equilibrium?

• A. $6L$
• B. $9L$
• C. $36L$
• D. None of the above

Answer 1

The correct option is A $6L$

The equilibrium reaction is $3A\left(g\right)+B\left(g\right)\rightleftharpoons 2C\left(g\right)$.

Let $V$ be the volume of the flask.

The equilibrium number of moles of $A,B$ and $C$ are $2,2$ and $2$ respectively.

The equilibrium concentrations of $A,B$ and $C$ are $\frac{2}{V},\frac{2}{V}$ and $\frac{2}{V}$ respectively.

The expression for the equilibrium constant is $K_c=\frac{[C{]}^2}{\left[A{]}^3\right[B]}.$

Substituting values in the above expression, we get
$9.0=\frac{(\frac{2}{V}{)}^2}{\left(\frac{2}{V}{)}^3\right(\frac{2}{V})}.$

Thus, $V=6L$.