Redox Recap
Electrode Potentials Worksheet
1. Oxidation Numbers
State the oxidation number of the following atoms.
a) Sulfur in SO₂
+4
b) Chromium in Cr₂O₇²⁻
+6
c) Sulfur in SO₄²⁻
+6
d) Manganate in MnO₄⁻
+7
e) Fluorine in SF₆
-1
f) Vanadium in VO²⁺
+4
g) Oxygen in H₂O₂
-1
h) Vanadium in VO₂⁺
+5
2. Half Equations
Write the half equation for the following reactions.
a) Vanadate (IV) being oxidised to Vanadate (V).
VO2+ + H2O
→
VO2+ + 2H+ + e–
b) Dichromate (VI) being reduced to chromium (III).
Cr2O72- + 14H+ + 6e–
→
2Cr3+ + 7H2O
c) Ethanedioate being oxidised to form carbon dioxide.
C2O42-
→
2CO2 + 2e–
d) Manganate (VII) being reduced to Manganese (II).
MnO4– + 8H+ + 5e–
→
Mn2+ + 4H2O
e) Chlorate (V) being reduced to chlorine.
2ClO3– + 12H+ + 10e–
→
Cl2 + 6H2O
3. Ionic Equations
Write the ionic equation for the following reactions.
a) Iron (II) reducing dichromate (VI) to chromium (III).
Half equations combined:
Cr2O72- + 14H+ + 6Fe2+
→
2Cr3+ + 7H2O + 6Fe3+
b) Manganate oxidising hydrogen peroxide to oxygen.
Half equations combined:
2MnO4– + 6H+ + 5H2O2
→
2Mn2+ + 8H2O + 5O2
c) Nitric acid oxidising copper to from copper (II).
(The nitrogen is reduced to form nitrogen (IV)).
Half equations combined:
Cu + 4H+ + 2NO3–
→
Cu2+ + 2NO2 + 2H2O
d) Chromium (III) being oxidised to form dichromate (VI) by Manganate (VII).
(The manganate is reduced to Mn2+ in the process).
Half equations combined:
10Cr3+ + 11H2O + 6MnO4–
→
5Cr2O72- + 22H+ + 6Mn2+