Question

1 mole of ${NO}_2$ and $2$ moles of $CO$ are enclosed in a one litre vessel to attain the following equilibrium ${NO}_2+CO\leftrightharpoons NO+{CO}_2$. It was estimated that at the equilibrium, $25\%$ of initial amount of $CO$ consumed. The equilibrium constant $K_p$ is:

• A. $1$
• B. $1/2$
• C. $1/4$
• D. $1/3$

Answer 1

Answer: (D)

$1/3$

1 mole of $N{O}_2$ reacts with 1 mole of CO ,Thus 25% of CO i.e $\left(\frac{1}{2}\right)$ moles out of 2 moles have reacted with 1/2 moles of $N{O}_2$

$K_c=\frac{\left(\frac{1}{2}\right)\left(\frac{1}{2}\right)}{\left(\frac{1}{2}\right)\left(\frac{3}{2}\right)}$

$=\frac{1}{3}$

$Kp=Kc(RT{)}^{\Delta n}$

Δn = change in no. of moles =no. of moles of product- no. of moles of reactant

$\Delta n=(1+1)-(1+1)=0$

Therefore,

$Kp=Kc=\frac{1}{3}$

Hence the correct option is D.