Grade 12 Physics (Chemistry) Term 2 Revision Guide
This guide focuses on the core themes of the CAPS curriculum for Paper 2: Organic
Chemistry, Rates of Reaction, Chemical Equilibrium, and Acids and Bases.
1. Organic Chemistry: Nomenclature and Physical Properties
Core Concepts
• Homologous Series: A series of organic compounds that can be described by the
same general formula and where each member differs from the next by a 𝐶𝐻2
group.
• Functional Groups: Atoms or groups of atoms that determine the chemical
properties of a molecule (e.g., -OH for alcohols).
• Intermolecular Forces (IMF): Physical properties like boiling point and vapour
pressure depend on the strength of IMFs.
o London forces (Induced dipole): Weakest, present in all molecules (e.g.,
alkanes).
o Dipole-dipole forces: Present in polar molecules (e.g., esters, aldehydes).
o Hydrogen bonding: Strongest, present in alcohols and carboxylic acids.
Practice Problem 1
An unknown compound has the molecular formula 𝐶3 𝐻6 𝑂2. It is a functional isomer of
ethyl methanoate.
1. Identify the homologous series to which this compound belongs.
2. Write down the IUPAC name for this compound.
3. Compare the boiling point of this compound to that of propan-1-ol. Explain the
difference by referring to intermolecular forces.
, Solution 1
1. The functional isomer of an ester (ethyl methanoate) is a carboxylic acid.
2. For a 3-carbon carboxylic acid: Propanoic acid.
3. Comparison and Explanation:
• Propanoic acid has a higher boiling point than propan-1-ol.
• Both molecules contain hydrogen bonding.
• However, carboxylic acids form stable “dimers” where two hydrogen bonds exist
between molecules, whereas alcohols form only one hydrogen bond per
functional group.
• More energy is required to overcome the stronger/more numerous intermolecular
forces in propanoic acid.
2. Chemical Equilibrium and 𝐾𝑐
Core Concepts
• Le Chatelier’s Principle: If a system at equilibrium is disturbed, the system will
reinstate a new equilibrium by favoring the reaction that opposes the disturbance.
• Equilibrium Constant (𝐾𝑐 ): A ratio of product concentrations to reactant
concentrations at equilibrium.
Practice Problem 2
Hydrogen gas and iodine gas react in a sealed 2 dm3 container at 400 ∘ C according to
the following balanced equation:
𝐻2 (𝑔) + 𝐼2 (𝑔) ⇌ 2𝐻𝐼(𝑔) Δ𝐻 < 0
Initially, 0.4 mol of 𝐻2 and 0.4 mol of 𝐼2 are placed in the container. At equilibrium, it is
found that 0.1 mol of 𝐻2 remains. Calculate the equilibrium constant 𝐾𝑐 at this
temperature.
Solution 2
To solve for 𝐾𝑐 , we use a RICE (Reaction, Initial, Change, Equilibrium) table.
• Step 1: Calculate initial concentrations or work in moles.
𝑉 = 2 dm3
• Step 2: Determine change in moles. Since 0.4 mol was initial and 0.1 mol
remains:
moles of 𝐻2 reacted = 0.4 mol − 0.1 mol = 0.3 mol
This guide focuses on the core themes of the CAPS curriculum for Paper 2: Organic
Chemistry, Rates of Reaction, Chemical Equilibrium, and Acids and Bases.
1. Organic Chemistry: Nomenclature and Physical Properties
Core Concepts
• Homologous Series: A series of organic compounds that can be described by the
same general formula and where each member differs from the next by a 𝐶𝐻2
group.
• Functional Groups: Atoms or groups of atoms that determine the chemical
properties of a molecule (e.g., -OH for alcohols).
• Intermolecular Forces (IMF): Physical properties like boiling point and vapour
pressure depend on the strength of IMFs.
o London forces (Induced dipole): Weakest, present in all molecules (e.g.,
alkanes).
o Dipole-dipole forces: Present in polar molecules (e.g., esters, aldehydes).
o Hydrogen bonding: Strongest, present in alcohols and carboxylic acids.
Practice Problem 1
An unknown compound has the molecular formula 𝐶3 𝐻6 𝑂2. It is a functional isomer of
ethyl methanoate.
1. Identify the homologous series to which this compound belongs.
2. Write down the IUPAC name for this compound.
3. Compare the boiling point of this compound to that of propan-1-ol. Explain the
difference by referring to intermolecular forces.
, Solution 1
1. The functional isomer of an ester (ethyl methanoate) is a carboxylic acid.
2. For a 3-carbon carboxylic acid: Propanoic acid.
3. Comparison and Explanation:
• Propanoic acid has a higher boiling point than propan-1-ol.
• Both molecules contain hydrogen bonding.
• However, carboxylic acids form stable “dimers” where two hydrogen bonds exist
between molecules, whereas alcohols form only one hydrogen bond per
functional group.
• More energy is required to overcome the stronger/more numerous intermolecular
forces in propanoic acid.
2. Chemical Equilibrium and 𝐾𝑐
Core Concepts
• Le Chatelier’s Principle: If a system at equilibrium is disturbed, the system will
reinstate a new equilibrium by favoring the reaction that opposes the disturbance.
• Equilibrium Constant (𝐾𝑐 ): A ratio of product concentrations to reactant
concentrations at equilibrium.
Practice Problem 2
Hydrogen gas and iodine gas react in a sealed 2 dm3 container at 400 ∘ C according to
the following balanced equation:
𝐻2 (𝑔) + 𝐼2 (𝑔) ⇌ 2𝐻𝐼(𝑔) Δ𝐻 < 0
Initially, 0.4 mol of 𝐻2 and 0.4 mol of 𝐼2 are placed in the container. At equilibrium, it is
found that 0.1 mol of 𝐻2 remains. Calculate the equilibrium constant 𝐾𝑐 at this
temperature.
Solution 2
To solve for 𝐾𝑐 , we use a RICE (Reaction, Initial, Change, Equilibrium) table.
• Step 1: Calculate initial concentrations or work in moles.
𝑉 = 2 dm3
• Step 2: Determine change in moles. Since 0.4 mol was initial and 0.1 mol
remains:
moles of 𝐻2 reacted = 0.4 mol − 0.1 mol = 0.3 mol
