Arrange the following, (i) CaH_(2), BeH_(2) and TiH_(2) in order of increasing electrical conductance. (ii) LiH, NaH, CsHis order of increasing ionic character(iii) H-H-D-D and F-F in order of increasing bond dissocation enthalpy. (iv) NaH, MgH_(2) and H_(2)O in order of increasing reducing property.

Arrange the following, (i) CaH_(2), BeH_(2) and TiH_(2) in order of in

1.	Arrange the following, (i) CaH_(2), BeH_(2) and TiH_(2) in order of increasing electrical conductance. (ii) LiH, NaH, CsHis order of increasing ionic character(iii) H-H-D-D and F-F in order of increasing bond dissocation enthalpy. (iv) NaH, MgH_(2) and H_(2)O in order of increasing reducing property.
Answer» Solution :(i) `BeH_(2)` is a covalenthydride, therefore, it does not conduct electricity at all. `CaH_(2)` conducts electricity in the FUSED statewhile `TiH_(2)` conducts electricity at room temperature. Thus, the order of increasing electrical conductance is : `BeH_(2) LT CaH_(2) lt TiH_(2)` (ii) Electronegativity decreases down the group from Li to Cs, therefore, the ionic CHARACTER of their hydrides increases in the same order, i.e., `LiH lt NaH lt CsH` (iii) Due to greater nuclear mass, the bondpair in D-D bond is attracted more strongly than in H-H bond. Therefore, bond dissociation energy of D-D bond is higher than that of H-H bond. However, due to repulsions between lone pairs of F and the bond pair, F-F bonddissociation enthalpy is the minimum . Thus the bond dissociation enthalpy increases in the order: ` F - F lt H -H lt D -D` (iv) Ionic hydrides are powerful reducing agents. Both `MgH_(2)` and `H_(2)O` are covalent hydrides but he bond dissociation energy of `H_(2)O` is much higher than that of `MgH_(2)` . Therefore, the reducing character increases in the order : `H_(2) O lt MgH_(2) lt NaH`