KI in acetone, undergoes S_N2 reaction with each of P, Q, R and S. The rates of the reaction vary as

The compound that does NOT liberate CO₂, on treatment with aqueous sodium bicarbonate solution, is

Consider the following complex ions : P, Q and R.

$$P = {[Fe{F_6}]^{3 - }}$$, $$Q = {[V{({H_2}O)_6}]^{2 + }}$$ and $$R = {[Fe{({H_2}O)_6}]^{2 + }}$$

The correct order of the complex ions, according to their spin-only magnetic moment values (in B.M.) is