At 298 K, for the equilibrium: \({\mathrm{PCl}}_{3}\left(\mathrm{g}\right)+{\mathrm{Cl}}_{2}\left(\mathrm{g}\right)⇄{\ma…

At 298 K, for the equilibrium:

\({\mathrm{PCl}}_{3}\left(\mathrm{g}\right)+{\mathrm{Cl}}_{2}\left(\mathrm{g}\right)⇄{\mathrm{PCl}}_{5}\left(\mathrm{g}\right)\)

Initial equilibrium concentrations are:
\(\left[{\mathrm{PCl}}_{3}\right]=0.20mol{L}^{-1}\\ \left[C{l}_{2}\right]=0.10mol{L}^{-1}\\ [{\mathrm{PCl}}_{5}]=0.40mol{L}^{-1}\\ {K}_{c}=20\)

Now, 0.20 mol L⁻¹ \({\mathrm{Cl}}_{2}\) is added. Find the new equilibrium concentration of \({\mathrm{PCl}}_{3}\)