Describe the following : - (i) The role of cryolite in electro metallurgy of aluminium. (ii) The role of carbon monoxide in the refining of crude nickel.

Describe the following : - (i) The role of cryolite in electro metallu

1.	Describe the following : - (i) The role of cryolite in electro metallurgy of aluminium. (ii) The role of carbon monoxide in the refining of crude nickel.
Answer» (i) In the metllurgy of aluminimum, purified `Al_(2)O_(3)` is mixed with cryolite lowers melting point of the mix and brings conductivity. (ii) CO-forms a volatile complex (Nickel tetralabonyl) `Ni +4 Co overset(300-350K)rarrNi(CO)_(4)` the carbonyl is subjected to higher temperature so that it is decomposed giving a pure metal. `Ni[CO] overset(450-41 K)rarrNi+4CO`.

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(i) Arrange the following compounds in an increasing order of basic strength : `C_(6)H_(5)NH_(2), C_(6)H_(5)N(CN_(3))_(2), (C_(2)H_(5))_(2)NH and CH_(3)NH_(2)` (ii) Arrange the following compounds in a decreasing order of `pK_(b)` values: `C_(2)H_(5)NH_(2), C_(6)H_(5)NHCH_(3), (C_(2)H_(5))_(2) NH and C_(6)H_(5)NH_(2)`
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Describe the following : - (i) The role of cryolite in electro metallurgy of aluminium. (ii) The role of carbon monoxide in the refining of crude nickel.

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