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.
The correct chemical formulae is CsBr
The columns of the periodic table, also referred to as "groups" contain elements with similar reactive properties, due to these elements having a similar configuration of electrons in their outer shell.