FINAL HSC Chemistry Revision Questions

What is the functional group characteristic of a carboxylic acid?

• -OH

• -CHO

• -COOH

• -COO-

Answer explanation

The functional group characteristic of a carboxylic acid is -COOH, which consists of a carbonyl group (C=O) and a hydroxyl group (-OH) attached to the same carbon atom. This distinguishes it from other functional groups.

Which statement best describes a system at dynamic equilibrium?

• The concentrations of reactants and products are equal.

• The macroscopic properties of the system are constant.

• The forward and reverse reactions have stopped.

• The activation energy of the forward reaction equals that of the reverse reaction.

Answer explanation

A system at dynamic equilibrium maintains constant macroscopic properties, such as concentration and pressure, even though the forward and reverse reactions continue to occur. Thus, the correct statement is that these properties are constant.

Atomic Absorption Spectroscopy (AAS) is an analytical technique used to determine the:

• Molecular structure of a compound.

• Molar mass of a substance.

• Functional groups in an organic molecule.

• Concentration of metal ions in a sample.

Answer explanation

Atomic Absorption Spectroscopy (AAS) is specifically designed to measure the concentration of metal ions in a sample by detecting the absorption of light by free atoms, making this the correct choice.

According to the Brønsted-Lowry theory of acids and bases, a base is a:

• Proton donor.

• Proton acceptor.

• Hydroxide ion producer.

• Substance that turns litmus paper red.

Answer explanation

According to the Brønsted-Lowry theory, a base is defined as a proton acceptor, meaning it can accept hydrogen ions (H+) from acids. This distinguishes it from other definitions of bases.

Which of the following polymers is formed through addition polymerisation?

• Nylon-6,6

• Terylene

• Polytetrafluoroethene

• A polypeptide

Answer explanation

Polytetrafluoroethene is formed through addition polymerisation, where monomers add together without the loss of any small molecules. In contrast, Nylon-6,6 and Terylene are formed through condensation polymerisation.

Consider the exothermic reaction at equilibrium: 2SO₂(g) + O₂(g) ⇌ 2SO₃(g). Which change will cause the equilibrium to shift to the left, increasing the yield of reactants?

• Increasing the pressure by decreasing the volume.

• Adding a catalyst.

• Increasing the temperature.

• Removing some SO₃ from the system.

Answer explanation

Increasing the temperature shifts the equilibrium to the left for an exothermic reaction, favoring the formation of reactants (SO₂ and O₂) and decreasing the yield of products (SO₃).

What is the correct IUPAC name for the molecule with the structure CH3CH(OH)CH2COOH?

• Butan-3-ol-1-oic acid

• 1-Carboxypropan-2-ol

• 2-Hydroxybutanoic acid

• 3-Hydroxybutanoic acid

Answer explanation

The molecule CH3CH(OH)CH2COOH has a hydroxyl group (OH) on the second carbon and a carboxylic acid (COOH) on the first carbon, making it 2-Hydroxybutanoic acid, which is the correct IUPAC name.

• 5.0

• 7.0

• 9.0

• 14.0

Answer explanation

To find the pH, first calculate the pOH: pOH = -log[OH-] = -log(1.0 x 10^-5) = 5.0. Then, use the relation pH + pOH = 14.0. Thus, pH = 14.0 - 5.0 = 9.0. The correct answer is 9.0.

Which pair of compounds are structural isomers?

• Ethene and ethyne

• Propan-1-ol and propanoic acid

• Butane and 2-methylpropane

• Hexane and cyclohexane

Answer explanation

Butane and 2-methylpropane are structural isomers because they have the same molecular formula (C4H10) but different structural arrangements of atoms. The other pairs do not meet this criterion.

A student wishes to distinguish between aqueous solutions of potassium carbonate and potassium sulfate. Which reagent would be most suitable to add to both solutions?

• Silver nitrate solution

• Dilute hydrochloric acid

• Barium nitrate solution

• Sodium hydroxide solution

Answer explanation

Barium nitrate solution is suitable because it reacts with sulfate ions to form a white precipitate of barium sulfate, allowing differentiation from potassium carbonate, which does not produce a precipitate with barium nitrate.