Although it is omitted, the reaction equation for the decomposition of phosphorus pentachloride is:
PCl₅ → PCl₃ + Cl₂
The equilibrium constant's equation then becomes:
Kc = [PCl₃]*[Cl₂] / [PCl₅]
Kc = (0.02 * 0.02) / 0.0095
Kc = 0.042
The equilibrium constant is 0.042.
Since the barium ion will be isoelectronic to the nearest noble gas, which is xenon, the electronic configuration for Ba2+ is: [Xe]

28%
Explanation:
mass of solute(KBr) = 3.73g
mass of solvent(H2O) = 131g
mass of solution = mass of solute + mass of solvent
= 3.73 + 131
= 134.73g

Thermodynamic quantity equivalent to the total heat content of a system It is equal to the internal energy of the system plus the product of pressure and volume