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Write short note on Ionic or Saline Hydrides. |
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Answer» Solution :These are stoichiometric compounds of dihydrogen formed with most of the s-block elements which are highly electropositive in character. Such as LiH, `BeH_2` and `MgH_2`. In fact `BeH_2` and `MgH_2` are polymeric in structure. The ionic hydrides are crystalline, non-volatile and non-conducting in solid state. However, their melts conduct electricity and on electrolysis liberate dihydrogen gas at anode, which confirms the existence of `H^-` ion. `2H^(-)` (melt) `overset"anode"to H_(2(g)) + 2e^(-)` Saline hydrides react violently with water producing dihydrogen gas. `NaH_((s)) + H_2O_((AQ)) to NaOH_((aq)) + H_(2(g))` Lithium HYDRIDE is RATHER unreactive at moderate temperatures with `O_2` or `Cl_2`. It is, THEREFORE, used in the SYNTHESIS of other useful hydrides, e.g., `8LiH+Al_2Cl_6 to 2LiAlH_4 + 6LiCl` `2LiH + B_2H_6 to 2LiBH_4` |
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