This in-depth summary for Unit 2 Electrochemistry is synthesized directly from the new
Ethiopian Grade 12 Chemistry curriculum It focuses on the relationship between electrical
energy and chemical change
1. Oxidation-Reduction Reactions (Redox) Electrochemistry begins with Redox reactions
which involve the transfer of electrons between species.
● Oxidation: The loss of electrons by a substance during a reaction.
● Reduction: The gain of electrons by a substance during a reaction.
● Oxidizing Agent: The substance that causes oxidation by accepting electrons and is
itself reduced.
● Reducing Agent: The substance that causes reduction by losing electrons and is
itself oxidized.
● Oxidation Number: A bookkeeping system used to keep track of electrons in a
reaction.
2. Balancing Redox Reactions The curriculum emphasizes balancing these equations
using the half-reaction method in both acidic and basic solutions.
● Acidic Solution: Balance atoms other than H and O then balance O with H2O and H
with H+ ions.
● Basic Solution: Follow the acidic steps then add OH- ions to both sides to neutralize
H+ ions.
3. Electrochemical Cells These are devices that convert chemical energy into electrical
energy or vice versa.
● Galvanic (Voltaic) Cells: Devices where spontaneous chemical reactions generate
electricity.
● The Anode: The electrode where oxidation occurs (negative in Galvanic cells).
● The Cathode: The electrode where reduction occurs (positive in Galvanic cells).
● Salt Bridge: An inverted U-tube containing a concentrated solution of an electrolyte
that maintains electrical neutrality by allowing ions to flow.
+2
● Cell Notation: A shorthand representation like Zn | Zn2+ || Cu2+ | Cu.
+1
,
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4. Standard Electrode Potentials (E0)
● Standard Hydrogen Electrode (SHE): The reference electrode used to measure the
potential of other electrodes assigned a value of 0.00 V.
+1
● Electromotive Force (EMF): The potential difference between the anode and
cathode.
+1
● Cell Potential Calculation: E cell = E cathode minus E anode.
+1
● Spontaneity: A reaction is spontaneous if the cell potential is positive and
non-spontaneous if it is negative.
+1
5. Electrolytic Cells These cells use electrical energy to drive a non-spontaneous chemical
reaction.
+1
● Electrolysis of Molten Salts: For example producing Sodium and Chlorine from
molten NaCl.
Ethiopian Grade 12 Chemistry curriculum It focuses on the relationship between electrical
energy and chemical change
1. Oxidation-Reduction Reactions (Redox) Electrochemistry begins with Redox reactions
which involve the transfer of electrons between species.
● Oxidation: The loss of electrons by a substance during a reaction.
● Reduction: The gain of electrons by a substance during a reaction.
● Oxidizing Agent: The substance that causes oxidation by accepting electrons and is
itself reduced.
● Reducing Agent: The substance that causes reduction by losing electrons and is
itself oxidized.
● Oxidation Number: A bookkeeping system used to keep track of electrons in a
reaction.
2. Balancing Redox Reactions The curriculum emphasizes balancing these equations
using the half-reaction method in both acidic and basic solutions.
● Acidic Solution: Balance atoms other than H and O then balance O with H2O and H
with H+ ions.
● Basic Solution: Follow the acidic steps then add OH- ions to both sides to neutralize
H+ ions.
3. Electrochemical Cells These are devices that convert chemical energy into electrical
energy or vice versa.
● Galvanic (Voltaic) Cells: Devices where spontaneous chemical reactions generate
electricity.
● The Anode: The electrode where oxidation occurs (negative in Galvanic cells).
● The Cathode: The electrode where reduction occurs (positive in Galvanic cells).
● Salt Bridge: An inverted U-tube containing a concentrated solution of an electrolyte
that maintains electrical neutrality by allowing ions to flow.
+2
● Cell Notation: A shorthand representation like Zn | Zn2+ || Cu2+ | Cu.
+1
,
Shutterstock
4. Standard Electrode Potentials (E0)
● Standard Hydrogen Electrode (SHE): The reference electrode used to measure the
potential of other electrodes assigned a value of 0.00 V.
+1
● Electromotive Force (EMF): The potential difference between the anode and
cathode.
+1
● Cell Potential Calculation: E cell = E cathode minus E anode.
+1
● Spontaneity: A reaction is spontaneous if the cell potential is positive and
non-spontaneous if it is negative.
+1
5. Electrolytic Cells These cells use electrical energy to drive a non-spontaneous chemical
reaction.
+1
● Electrolysis of Molten Salts: For example producing Sodium and Chlorine from
molten NaCl.
