Balance the following redox equation.
Cu(s) + H+(aq) + SO42−(aq) → Cu2+(aq) + H2O(l) + SO2(g)
Cu in Cu has oxidation state of 0
Cu in Cu+2 has oxidation state of +2
So, Cu in Cu is oxidised to Cu+2
S in SO4-2 has oxidation state of +6
S in SO2 has oxidation state of +4
So, S in SO4-2 is reduced to SO2
Reduction half cell:
1 SO4-2 + 2e- --> 1 SO2
Oxidation half cell:
1 Cu --> 1 Cu+2 + 2e-
Number of electrons is same in both half reactions.
So, balancing of electrons is not required. It's already balanced
Lets combine both the reactions.
1 SO4-2 + 1 Cu --> 1 SO2 + 1 Cu+2
Balance Oxygen by adding water
1 SO4-2 + 1 Cu --> 1 SO2 + 1 Cu+2 + 2 H2O
Balance Hydrogen by adding H+
1 SO4-2 + 1 Cu + 4 H+ --> 1 SO2 + 1 Cu+2 + 2 H2O
This is balanced chemical equation in acidic medium
SO4-2 + Cu + 4 H+ --> SO2 + Cu+2 + 2 H2O
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