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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. |
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Answer» 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)`. |
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