Choose correct statements (s) regarding the following reactions.
`Cr_(2)O_(7)^(2-)(aq)+3SO_(3)^(2-)(aq)+8H^(+) rarr 2Cr^(3+)(aq)+3SO_(4)^(2-)(aq)+4H_(2)O`

Options

A. `Cr_(2)O_(7(aq))^(2-)+3SO_(2(g))+2H_((aq))^(+)rarr 2Cr_((aq))^(3+) rarr 2Cr_((aq))^(3+)+3SO_(4(aq))^(2-)+H_(2)O_((l))`
B. `2Cr_(2)O_(7(aq))^(2-)+3SO_(2(g))+4H_((aq))^(+)rarr 4Cr_((aq))^(3+)+3SO_(4(aq))^(2-)+2H_(2)O_((l))`
C. `Cr_(2)O_(7(aq))^(2-)+3SO_(2(g))+14H_((aq))^(+)rarr 2Cr_((aq))^(3+)+3SO_(4(aq))^(2-)+7H_(2)O_((l))`
D. `Cr_(2)O_(7(aq))^(2-)+6SO_(2(g))+7H_((aq))^(+)rarr 2Cr_((aq))^(3+)+6SO_(4(aq))^(2-)+7H_(2)O_((l))`

Answer

A

Explanation

`Cr_(2)O_(7)^(2-)+SO_(2)rarrCr^(3+)+SO_(4)^(2-)` ( in acidic solution)
Oxidation half equation :
`SO_(2)+2H_(2)O rarr SO_(4)^(2-)+4H^(+)+2e^(-)` ...(i)
Reduction half equation :
`Cr_(2)O_(7)^(2-)+14H^(+)+6e^(-)rarr 2 Cr^(3+)+7H_(2)O` ...(ii)
Multiplying eqn. (i) by 3 and adding to eqn. (ii) we get
`Cr_(2)O_(7)^(2-)+3SO_(2)+2H^(+) rarr 2 Cr^(3+)+3SO_(4)^(2-)+H_(2)O`