Which of the following is/are correct about ionic hydrides?
Which of the following is/are correct about ionic hydrides?
The correct options are
A They are good conductors of electricity in fused state
B They are good reducing agents
C They are more densely packed than their parent metals
D The crystal structures of ionic hydrides show no evidence of directional bonding
Alkali metals and heavier alkaline earth metals like Ca, Sr and Ba, combine with Hydrogen at high temperatures to form Ionic compounds. These metal-hydrides are usually heavier than the corresponding metals as the H− ions occupy the holes in the lattice without distorting the structure. Further, the crystal structures of such compounds no signs of directional bonding and they are always stoichiometric. In fused state, these ionic hydrides conduct electricity and H2 is liberated at the anode where H− ions are oxidized to molecular hydrogen.
Let us look at some of the properties of these hydrides:
a.)Except for LiH, which is not completely ionic, the other hydrides (group I and group II) decompose into their constituent elements on pyrolysis.
b.)The H− ion is not stable in water and hence these ionic hydrides vigorously react with water liberating Hydrogen
i.)NaH+H2O→NaOH+H2
c.)Lithium hydride is unreactive at room temperature and hence used in synthesis of other useful hydrides
i.)8LiH+Al2Cl6→2LiAlH4+6LiCl
ii.)2LiH+B2H6→2LiBH4 (Display the reactions on screen)
d.)Be Mg B and Al hydrides are polymeric in nature
So, all the options are correct.
A
They are good conductors of electricity in fused state
B
They are good reducing agents
C
They are more densely packed than their parent metals
D
The crystal structures of ionic hydrides show no evidence of directional bonding
Alkali metals and heavier alkaline earth metals like Ca, Sr and Ba, combine with Hydrogen at high temperatures to form Ionic compounds. These metal-hydrides are usually heavier than the corresponding metals as the H− ions occupy the holes in the lattice without distorting the structure. Further, the crystal structures of such compounds no signs of directional bonding and they are always stoichiometric. In fused state, these ionic hydrides conduct electricity and H2 is liberated at the anode where H− ions are oxidized to molecular hydrogen.
Let us look at some of the properties of these hydrides:
a.)Except for LiH, which is not completely ionic, the other hydrides (group I and group II) decompose into their constituent elements on pyrolysis.
b.)The H− ion is not stable in water and hence these ionic hydrides vigorously react with water liberating Hydrogen
i.)NaH+H2O→NaOH+H2
c.)Lithium hydride is unreactive at room temperature and hence used in synthesis of other useful hydrides
i.)8LiH+Al2Cl6→2LiAlH4+6LiCl
ii.)2LiH+B2H6→2LiBH4 (Display the reactions on screen)
d.)Be Mg B and Al hydrides are polymeric in nature
So, all the options are correct.
