(a) (i) Which types of orescan be concentrated by froth floatation method? Give two examples for such ores. (ii) Explain the variation in E_(M^(3+)//M^(2+))^(@) 3d series.

(a) (i) Which types of orescan be concentrated by froth floatation met

1.	(a) (i) Which types of orescan be concentrated by froth floatation method? Give two examples for such ores. (ii) Explain the variation in E_(M^(3+)//M^(2+))^(@) 3d series.
Answer» Solution :(a) (i) Sulphide ores can be concentrated by froth floatation method. e.g., (7) Copper PYRITES `(CuFeS^(2)) (77)` Zinc blende (ZNS) (Hi) Galena (PbS) (II) In transition series, as we move down from Ti to Zn, the standard reduction `E_(M^(2+)//M^(3+))^(@)` values is approaching towards left negative value and copper has a reduction potential. i.e. element copper is more STABLE than `Cu^(2+)`. (ii) `E_(M^(2+)//M)^(@)` value for manganese and zinc are more negative than REGULAR trend. to extra stability arises due to the half filled `d^(5)` configuration in `Mn^(2+)` and completely filled `d^(10)` configuration in `Zn^(2+)`. (iii) The standard electrode potential for the `M^(3+)//Mn^(2+)` half cells give the relative stability between `M^(3+)` and `M^(2+)` (iv) The high reduction potential of `Mn^(3+)// Mn^(2+)` indicates `Mn^(2+)` is more stable than `Mn^(3+)`. (v) For `Fe^(3+)//Fe^(2+)` the reduction potential is 0.77 V, and this how low value indicates that both `Fe^(3+)` and `Fe^(2+)` can exist under normal condition. (vi) `Mn^(3+)` has a `3d^(4)` configuration while that of `Mn^(2+)` is `3d^(5)`. The extra stability associated with a half filled d sub-shell makes the reduction of `Mn^(3+)` very feasible `[E^(@) = +1.51 V]`