Dissociation of `PCl_(5)` decreases in presence of increase in `Cl_(2)` why ?

Phosphorus pentachloride dissociates as follows in a closed vesselm PCl_(5)(g)hArr PCl_(3)(g)+Cl_(2)(g) . If total pressure at equilibrium of the reaction mixture is P and degree of dissociation of PCl_(5) is x, the partial pressure of PCl_(3) will be :

Solid PCl_(5) exists as :

Why does ionisation energy of alkali metals decreases with the increase in atomic number?

Ammoniacal solution of MgSO_(4) in presence of NH_(4)Cl is heated with Na_(2)HPO_(4) , a white precipitate is formed of

The shape of PCl_5 is

The system PCl_(5)(s)hArr PCl_(3)(g)+Cl_(2)(g) attains equilibrium. If the equilibrium concentration of PCl_(3)(g) is doubled, the concentration of Cl_(2)(g) would become :

Toluene reacts with Cl_(2) in presence of light to give