Assign reasons for the following :

1. (i) SF6 is kinetically inert.

2. (ii) NF3 is an exothermic compound whereas NCl3 is not.

(iii) HCl is a stronger acid than HF though fluorine is more electronegative than chlorine.

1. Due to the presence of 6 F atoms around S in SF6, it is difficult for an attacking agent to attack it, hence it is kinetically inert.
2. The bond dissociation enthalpy of F2 is less than that of Cl2 (due to interionic repulsions in F2). Thus less energy is required to break F-F bonds. The N-F bond is stronger than the N-Cl bond, hence more energy is released during the formation of NF3. Combining the two factors, i.e. low energy required and high energy released, formation of NF3 leads to release of energy(Exothermic) whereas due to high energy required and low energy released, NCl3 requires energy to form(endothermic)
3. Due to larger size of Cl, the H-Cl bond is weaker than H-F bond and hence release of H⁺ from HCl is easier