(a) Following are the transition metal ions of 3d series:
`Ti^(4+),V^(2+),Mn^(3+),Cr^(3+)`
(Atomic numbers: `Ti=22,V=23,Mn=25,Cr=24`)
Answer the following:
(i) Which ion is most stable in an aqueous solution and why?
(ii) Which ion is a strong oxidising agent and why?
(iii) Which ion is colourless and why?
(b) Complete the following equations:
(i) `2MnO_(4)^(-)+16H^(+)+5S^(-)to`
(ii) `KMnO_(4)overset(heat)to`

Explanation

(a) `Ti^(4+)=3d^(@),V^(2+)=3d^(3),Mn^(3+)=3d^(4),Cr^(3+)=3d^(3)`
Out of these four ions,`Cr^(3+)` is most stable due to crystal field splitting concept. In `Cr^(3+),t_(2)g` in half-filled. Hence, is extra stable.
(ii) `Mn^(3+)` is strong oxidising agent because `Mn^(3+)` can easily be converted into `Mn^(2+)` having `d^(5)` configuration which is stable half-filled configuration. ltBrgt (iii) `Ti^(4+)` is colourless because it is having no unpaired `e^(-)` for excitation to higher energy level and it is colourless.
(b) (i) `2MnO_(4)^(-)+16H^(+)+5S^(2)to2Mn^(2+)+8H_(2)O+5S`
(ii) `2KMnO_(4)overset(Delta)tounderset(("Pot. manganate"))(K_(2)MnO_(4)+MnO_(2))+O_(2)`