Balance the following redox reactions by ion electron method.
Cr2O2−7+SO2(g)→Cr3+(aq)+SO2−4(aq) (in acidic solution)
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Solution
The oxidation half reaction is SO2(g)+2H2O(l)→SO2−4+4H+(aq)+2e−. The reduction half reaction is Cr2O2−7(aq)+14H+(aq)+6e−→2Cr3+(aq)+7H2O(l). The oxidation half reaction is multiplied by 3 and added to the reduction half reaction to obtain the balanced redox reaction. Cr2O2−7+3SO2(g)+2H+(aq)→2Cr3+(aq)+3SO2−4(aq)+H2O(l)