Arrange the following
a.`CaH_(2),BeH_(2)`and `TiH_(2)` in order of increasing electrical conductance.
b. `LiH,NaH` and `CsH` in order of increasing ionic character.
c. `H-H,D-D` and `F-F` in order of increasing bond dissociaton enthalpy.
d. `NaH,MgH_(2)` and `H_(2)O` in order of increasing reducing property.

Explanation

a. The order of increasing electric conductance is
`BeH_(2)ltCH_(2)ltTiH_(2)`
Skince `CaH_(2)` is an ionic hydride, it conducts electricity in fused state, `BeH_(2)` being covalent hydride does not conduct electricity at all. `TiH_(2)`, a metallic hydride conducts electricity at room temperature.
b. The order of increasing ionic character is
`LiHltNaHltCsH`
Down the group `(darr)`, from `Li` to `Cs`, electronegativity decreases adn and hence ionic character increases.
c. Order of increasing bond dissociation enthalpy:
`F-FltH-HltD-D`
Due to greater nucleus mass, the bond pair in `D-D` bond is attracted more strongly than in `H-H` bond. Thus, the bond dissociation enthalpy of `D-D` is higher than `H-H` bond. However, due to repulsion between lone pairs of `F` and the bond, `F-F` bond dissociation enthalpy is the minimum, and hence the order.
d. Order of increasing reducing property:
`H_(2)OltMgH_(2)ltNaH`
`NaH` is ionic hydride whereas `H_(2)O` adn `MgH_(2)` are covalent hydrides. Ionic hydrides are stronger reducing agent as compared to covalent hydrides. Hence `NaH` is stronger reducing agent as compared to `H_(2)O` and `MgH_(2)`. Out of `H_(2)O` and `MgH_(2)`, hence `H_(2)O` is weaker reducing agent as compared to `MgH_(2)`.