In Which case (s), there is change in oxidation number ?

Options

A. Aqueous solution of `CrO_(4)^(2-)` is acidified
B. `SO_(2)` gas is passed through acidified `Cr_(2)O_(7)^(2-)` solution
C. `Cr_(2)O_(7)^(2-)` solution is made alkaline
D. `CrO_(2)Cl_(2)` is is dissolved in NaOH.

Answer

B

Explanation

(a) `2overset(+6)(Cr)O_(4)^(2-)+2H^(+)rarroverset(+6)Cr_(2)O_(7)^(2-)+H_(2)O " "("no change")`
`overset(+6)Cr_(2)O_(4)^(2-)+3overset(+4)SO_(2)+2H^(+)rarr2overset(+3)Cr^(3+)+3overset(+6)SO_(4)^(2-)+H_(2)O" "("change")`
`overset(+6)Cr_(2)O_(7)^(2-)+2OH^(-)rarr2overset(+6)CrO_(4)^(2-)+H_(2)O" "("no change")`
`overset(+6)CrO_(2)Cl_(2)+2NaOHrarrNaoverset(+6)CrO_(4)+2HCl" "("no change")`.