Chemistry - Chemical Equilibrium Question with Solution | TestHub

$$\begin{array}{c}\text{Take}\text{R}\text{=}\text{0.0821}\text{L}\text{atm/mol/K}\text{and}\text{T}\text{=}\text{546}\text{K}{\text{n}}_{\text{total}}\text{=}\text{PV/RT}\text{=}\\ \text{(4.8)(112)/[(0.0821)(546)]}\text{=}\text{12,}\text{so}\text{(c)}\text{is}\text{correct}\\ \text{Let}\text{x}\text{mol}\text{of}{\text{PCl}}_{\text{5}}\text{dissociate:}\text{4}\text{+}\text{(5}\text{-}\text{x)}\text{+}\text{x}\text{+}\text{x}\text{=}\text{12,}\text{so}\text{x}\text{=}\text{3}\\ \alpha \text{=}\text{3/5}\text{=}\text{0.6,}\text{so}\text{(a)}\text{is}\text{correct}\\ \text{Moles}\text{at}\text{equilibrium:}{\text{PCl}}_{\text{5}}\text{=}\text{2,}{\text{PCl}}_{\text{3}}\text{=}\text{3,}{\text{Cl}}_{\text{2}}\text{=}\text{3,}\text{Ar}\text{=}\text{4}\\ \text{Partial}\text{pressures:}{\text{P}}_{\text{PCl5}}\text{=}\text{4.8(2/12)}\text{=}\text{0.8}\text{atm,}{\text{P}}_{\text{PCl3}}\text{=}{\text{P}}_{\text{Cl2}}\text{=}\text{4.8(3/12)}\text{=}\text{1.2}\\ \text{atm}\\ {\text{K}}_{\text{P}}\text{=}\text{(1.2)(1.2)/0.8}\text{=}\text{1.8}\text{atm,}\text{so}\text{(b)}\text{is}\text{wrong}\\ \text{Removing}\text{Ar}\text{at}\text{constant}\text{pressure}\text{reduces}\text{the}\text{volume,}\text{which}\text{favours}\text{fewer}\text{moles}\\ \text{of}\text{gas,}\text{so}\text{dissociation}\text{decreases}\text{and}\text{(d)}\text{is}\text{wrong}\\ \text{The}\text{correct}\text{statements}\text{are}\text{(a)}\text{and}\text{(c).}\end{array}$$