(a) Account for the following :
(i) Oxidising power in the series `VO^(2+)ltCr_(2)O_(7)^(2-)lt MnO_(4)^(-)`.
(ii) Actinoid contraction is greater from element to element than lanthanoid contraction.
(iii) Oxoanions of a metal show higher oxidation state.
(b) What is Misch metal ? Give its one use.

Explanation

(a) (i) The oxidising power of the species varies in the order :
`VO^(2+)lt Cr_(2)O_(7)^(2-)lt MnO_(4)^(-)`
This is explained on the basis of increasing stability of the lower species to which they are reduced.
(ii) Actinoid contraction is greater from element to element than lanthanoid contraction due to poor shielding of 5f electrons compared to that of 4f electrons in lanthanoids.
(iii) Oxoanions of a metal shows higher oxidation state due to the ability of oxygen to form multiple bonds and its high electronegativity.
(b) Misch metal is an alloy 95% of a lanthanoid metal and 5% iron with traces of S, C, Ca and Al.
Use: To produce bullets, shell and lighter flint.