Question

Question 9.16 Arrange the following

(i) CaH2, BeH2 and TiH2 in order of increasing electrical conductance.

(ii) LiH, NaH and CsH in order of increasing ionic character.

(iii) H–H, D–D and F–F in order of increasing bond dissociation enthalpy.

(iv) NaH, MgH2 and H2O in order of increasing reducing property.

Class XI Hydrogen Page 289

Answer 1

(i) ionic character is directly proportional to electrical conductance .
So, order of ionic character Be < Ca < Ti ( size of cation increases )
Hence, order of electrical conductance is BeH2 < CaH2 < TiH2

(ii) ionic character is directly proportional to size of cation.

Order of size of cation is Li < Na < Cs ; so,order of Ionic character is LiH < NaH < CsH

(iii) bond length is inversely proportional to bond dissociation enthalpy.
order of bond length is D < H <F
So, order of bond dissociation enthalpy is F-F < H-H < D-D

(iv) metal hydrides are stronger reducing agents than non metal hydrides.
so, order of reducing agents is H2O < MgH2 < NaH