b) Balance O atoms with water. Not needed.
c) Balance H atoms with H+. Not needed
d) Balance charge with electrons.
2 I - I2 + 2 e-
Step #3 Multiply each half-reaction by some integer to balance the # e- !
3(2I - I2 + 2 e-)
6 I- 3 I2 + 6 e-
Step #4 Add the half-reactions together, canceling things that are on
both sides of the equation:
6 e- + 14 H+ + Cr2O72- 2 Cr3+ + 7 H2O
6 I - 3 I2 + 6 e-
6 I -(aq) + 14 H+(aq) + Cr2O72-(aq) 3 I2 (s) + 7 H2O(L) + 2 Cr3+(aq)
Step #5 Check:_
Balancing Redox Equations in Acid
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