The oxidation number of
N increases from
−2 to
+2. The oxidation number of
Cl decreases from
+5 to
−1. Hence, hydrazine is the reducing agent and chlorate ion is the oxidizing agent.
Ion-electron method:
The oxidation half reaction is
N2H4(l)→NO(g)Balance the N atoms.
N2H4(l)→2NO(g)To balance oxidation number, add 8 electrons.
N2H4(l)→2NO(g)+8e−Add 8 hydroxide ions are to balance the charge.
N2H4(l)+8OH−(aq)→2NO(g)+8e−The reduction half reaction is
ClO−3(aq)→Cl−(aq)Add 6 electrons to balance the oxidation number.
ClO−3(aq)+6e−→Cl−(aq)Add 6 hydroxide ions to balance the charge.
ClO−3(aq)+6e−→Cl−(aq)+6OH−(aq)Multiply the oxidation half reaction by 3 and multiply the reduction half reaction by 2. Add two half reactions obtain the
balanced chemical equation.
3N2H4(aq)+4ClO−3(aq)→6NO(s)+4Cl−(aq)+6H2O(aq)Oxidation number method:
Total decrease in oxidation number of N is 8. Total increase in the oxidation number of Cl is 6.
Multiply
N2H4 with 3 and multiply
ClO−3 with 4.
3N2H4(l)+4ClO−3(aq)→NO(g)+Cl−(aq)Balance N and Cl atoms.
3N2H4(l)+4ClO−3(aq)→6NO(g)+4Cl−(aq)Balance the O atoms are by adding 6 water molecules.
3N2H4(l)+4ClO−3(aq)→6NO(g)+4Cl−(aq)+6H2O(l)This is the balanced chemical equation.