The equilibrium concentrations of $\mathrm{N}_2, \mathrm{H}_2$ and $\mathrm{NH}_3$ in the formation of $\mathrm{NH}_3$ at $500 \mathrm{~K}$ are $1.25 \times 10^{-2} \mathrm{M}, 4.0 \times 10^{-2} \mathrm{M}$ and $1.6 \times 10^{-2} \mathrm{M}$ respectively. The equilibrium constant $\mathrm{K}_{\mathrm{p}}$ at the same temperature is

• A

  $3.2(\mathrm{RT})^{-2}$
• B

  $32(\mathrm{RT})^2$
• C

  $320(\mathrm{RT})^2$
• Correct answer
  D

  $320(\mathrm{RT})^{-2}$

Hence, the correct answer is option: 'D'.