Question

Account for the following : Write the answers in four or five sentences only 

(i) The experimentally determined N-F bond length in NF₃ is greater than the sum of the single bond covalent radii of N and F. 

(ii) Mg₃N₂ when reacted with water gives off NH₃ but HCI is not obtained from MgCl₂ on reaction with water at room temperature. 

(iii) (SiH₃)₃N is a weaker base than (CH₃)₃N

Answer 1

(i) The size of nitrogen and fluorine are smaller and they have higher value of electron density. Thus, they repel the bond pair and show higher bond length as N-F bond

(ii) Mg₃N₂ + 6H₂O → 3Mg(OH)₂ + 2NH₃

MgCl₂ salt acts as stronger electrolyte so it is not hydrolysed. 

(iii) In (SiH₃)₃N lone pairs of electrons are used in p - π and d-π back bonding while; in (CH₃)₃N, such p - π, d - π bonding is not possible due to absence of vacant d-orbital in carbon. 

Hence, (CH₃)₃N is more basic than (SiH₃)₃N