Core
Reactions: Balancing Redox Equations
Slide 5 of 29
Balancing
Acidic-medium Redox Reaction: Method of Half-reactions
Though redox reactions can take place in both acidic and basic
mediums, you are required only learn to balance those that take
place in acidic medium.
Example 1:
The following reaction takes place in an acidic medium.
Cr2O72- (aq) + Cl- (aq) ® Cr3+ (aq) + Cl2 (g)
In this reaction, experimental evidence shows the consumption of
H+.
–In
other words, with a redox reaction occurring in an acidic medium, H+ ions could be one of the reactants.
Essentially, the chloride ions get oxidized to chlorine, for
which the half-equation would be
2Cl- ® Cl2 +
2e-
And the dichromate(VI) ions get reduced to chromium(III) ions,
and so the half-equation would be
Cr2O72- + 6e- ®
2Cr3+