Cr2O7^{2-} + 14H^{+} + 6e = 2Cr^{3+} + 7H2O  |1     

2I^{-} - 2e = I2                                              |3

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Cr2O7^{2-} + 14H^{+} + 6I^{-} = 2Cr^{3+} + 7H2O + 3I2

K2Cr2O7+6NaI+7H2SO4=Cr2(SO4)3+I2+K2SO4+3Na2SO4 +7H2O

Verified answer

K2Cr2O7+6NaI+7H2SO4=Cr2(SO4)3+3I2+K2SO4+3Na2SO4+7H2O

Cr(6+)+3e=Cr(3+)|3| 2

2I(-)-2e=I2(0)     |2| 3

Cr2O7(2-)+6I(-)+14H(+)=2Cr(3+)+3I2+7H2O