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MDCAT Chemistry QUESTION #7786
Question 1

The unit of equilibrium constant \(K_c\) for \(\mathrm{PCl}_5 \rightleftharpoons \mathrm{PCl}_3 + \mathrm{Cl}_2\) is:

  • \(\mathrm{dm}^3/\mathrm{mol}\)✔️
  • \(\mathrm{mol}/\mathrm{dm}^3\)
  • \(\mathrm{mol}/\mathrm{dm}^6\)
  • \(\mathrm{mol}^2/\mathrm{dm}^6\)
Correct Answer Explanation

\(\Delta n_g = (1+1)-1 = 1\). \(K_c = \frac{[\mathrm{PCl}_3][\mathrm{Cl}_2]}{[\mathrm{PCl}_5]}\) → units: \((\mathrm{mol}\ \mathrm{dm}^{-3})^2 / (\mathrm{mol}\ \mathrm{dm}^{-3}) = \mathrm{mol}\ \mathrm{dm}^{-3} = \mathrm{dm}^3/\mathrm{mol}\).