Electrochemistry

1. 1
Oxidation–Reduction Reactions
Electrochemistry-1
By: Dr. Munawar Hussain
Chemistry at Work

2. Everyday Oxidation-Reduction
Reactions
An oxidation–reduction reaction
 provides us with energy from food
 provides electrical energy in batteries
 occurs when iron rusts
4Fe(s) + 3O2(g) 2Fe2O3(s)
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3. Transfer of Electrons
An oxidation–reduction reaction
 transfers electrons from one reactant to another
Oxidation Is a Loss of electrons (OIL)
Zn(s) Zn2+(aq) + 2e
Reduction Is a Gain of electrons (RIG)
Cu2+(aq) + 2e Cu(s)
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4. Oxidation and Reduction
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5. Oxidized or Reduced?
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6. Zn and Cu2+
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oxidation
Zn(s) Zn2+(aq) + 2e-
Silvery metal
reduction
Cu2+(aq) + 2e- Cu(s)

7. ElectronTransfer from Zn to
Cu2+
Oxidation: electron loss
Reduction: electron gain
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8. Learning Check
Identify each of the following as:
1) oxidation or 2) reduction
A. Sn(s) Sn4+(aq) + 4e−
B. Fe3+(aq) + 1e− Fe2+(aq)
C. Cl2(g) + 2e− 2Cl−(aq)
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9. Solution
Identify each of the following as:
1) oxidation or 2) reduction
1 A. Sn(s) Sn4+(aq) + 4e−
2 B. Fe3+(aq) + 1e− Fe2+(aq)
2 C. Cl2(g) + 2e− 2Cl−(aq)
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10. Writing Oxidation and
Reduction Reactions
Write the separate oxidation and reduction reactions
for the following equation.
2Cs(s) + F2(g) 2CsF(s)
Each cesium atom loses an electron to form a cesium
ion.
2Cs(s) 2Cs+(s) + 2e− oxidation
Each fluorine atom gains an electron to form a fluoride
ion.
F2(s) + 2e– 2F−(s) reduction
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11. Learning Check
In light-sensitive sunglasses, UV light initiates an
oxidation–reduction reaction.
uv light
Ag+ + Cl− Ag + Cl
A. Which reactant is oxidized?
B. Which reactant is reduced?
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12. Solution
In light-sensitive sunglasses, UV light initiates
an oxidation-reduction reaction.
uv light
Ag+ + Cl− Ag + Cl
A. Which reactant is oxidized?
Cl − Cl− Cl + 1e−
B. Which reactant is reduced?
Ag+ Ag+ + 1e− Ag
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13. Learning Check
Identify the substances that are oxidized and
reduced in
each of the following reactions:
A. Mg(s) + 2H+(aq) Mg2+(aq) + H2(g)
B. 2Al(s) + 3Br2(g) 2AlBr3(s)
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14. Solution
Identify the substances that are oxidized and reduced in
each of the following reactions:
A. Mg is oxidized Mg(s) Mg2+(aq) + 2e−
H+ is reduced 2H+ + 2e− H2
B.Al is oxidized 2Al 2Al3+ + 6e−
Br is reduced 2Br + 2e− 2Br−
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15. Oxidation–Reduction in
Biological Systems
In biological systems, oxidation may involve
 the loss of H
 the gain of O
In biological systems, reduction may involve
 the gain of H
 the loss of O
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16. Oxidation–Reduction in Biological Systems
(continued)
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17. Summary of Oxidation and
Reduction
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