GCSE CHEMISTRY 8462/2H EXAM with Questions
and Answers/Plus a Rationale Updated 2026 A+/Instant
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EXAM COVERAGE
1. Rates of reaction and energy changes
2. Organic chemistry (hydrocarbons, polymers, alcohols, carboxylic acids)
3. Chemical analysis (chromatography, purity, gas identification)
4. Chemistry of the atmosphere (gases, pollutants)
5. Using resources (potable water, corrosion, ceramics, polymers)
1. A student investigates the rate of reaction between marble chips and hydrochloric acid. If 5.0 g
of small marble chips are replaced with 5.0 g of large marble chips while keeping all other
variables constant, what effect does this have on the rate and why?
A. The rate increases because the reaction is more exothermic.
B. The rate decreases because the total surface area of the reactant is smaller.
C. The rate remains the same because the total mass of the reactant is constant.
D. The rate increases because the frequency of successful collisions per second is higher.
CORRECT ANSWER : B
Rationale: Decreasing the size of the marble chips decreases the surface area exposed to the
acid, resulting in fewer collisions per second between reactant particles; therefore, the rate
decreases. A is incorrect because surface area does not change reaction enthalpy. C is incorrect
as rate depends on surface area, not just mass. D is incorrect as the frequency of collisions
decreases, not increases.
2. In the Haber process, the reaction is $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$ with a
$\Delta H = -92\text{ kJ/mol}$. Which condition set would produce the highest yield of
ammonia at equilibrium?
, A. High pressure and high temperature.
B. Low pressure and low temperature.
C. High pressure and low temperature.
D. Low pressure and high temperature.
CORRECT ANSWER : C
Rationale: According to Le Chatelier's Principle, increasing pressure favors the side with fewer
moles of gas (2 vs 4), and decreasing temperature favors the exothermic direction (forward). A
and D are incorrect because high temperature shifts the equilibrium back to reactants. B is
incorrect because low pressure reduces the yield.
3. Which of the following correctly describes the process of fractional distillation of crude oil?
A. It separates hydrocarbons based on their different melting points.
B. It involves chemical reactions that break down long-chain molecules into smaller ones.
C. It separates a mixture into fractions based on the different boiling points of the hydrocarbons.
D. It produces pure elements from crude oil through electrolysis.
CORRECT ANSWER : C
Rationale: Fractional distillation relies on the physical property of boiling points to separate
crude oil into fractions. A is incorrect because it is based on boiling points, not melting points. B
describes cracking, not distillation. D is incorrect as it is a physical separation, not chemical
synthesis.
4. During the combustion of an alkene, why does the flame appear more smoky or yellow
compared to an alkane of similar length?
A. Alkenes contain a higher percentage of carbon by mass, requiring more oxygen for complete
combustion.
B. Alkenes are more reactive and burn more slowly.
C. Alkenes contain ionic bonds that interfere with the flame.
D. Alkenes always undergo complete combustion.
CORRECT ANSWER : A
, Rationale: Alkenes have a higher carbon-to-hydrogen ratio than alkanes, meaning they require
more oxygen to burn completely; incomplete combustion produces soot (carbon particles). B, C,
and D are factually incorrect regarding combustion characteristics.
5. A student performs paper chromatography to identify food dyes. If a specific dye moves 4.2 cm
and the solvent front moves 7.0 cm, what is the $R_f$ value?
A. 0.60
B. 1.67
C. 0.58
D. 0.70
CORRECT ANSWER : A
Rationale: The $R_f$ value is calculated as the distance moved by the substance divided by the
distance moved by the solvent front ($4.2/7.0 = 0.60$). B, C, and D are mathematical errors in
division.
6. Which property of a hydrocarbon increases as the length of the carbon chain increases?
A. Volatility
B. Flammability
C. Viscosity
D. Rate of evaporation
CORRECT ANSWER : C
Rationale: As chain length increases, intermolecular forces become stronger, making the liquid
more viscous. Volatility, flammability, and rate of evaporation all decrease as chain length
increases.
7. How can the presence of water be confirmed in a chemical sample using a simple chemical test?
A. Add sodium hydroxide and look for a precipitate.
B. Use anhydrous copper(II) sulfate; it will turn from white to blue.
C. Pass the gas through limewater and look for cloudiness.
D. Test the pH using universal indicator.
, CORRECT ANSWER : B
Rationale: Anhydrous copper(II) sulfate is a classic test for water, where the addition of water
causes hydration, changing the color from white to blue. A, C, and D are tests for different
substances (metal ions, $CO_2$, and acidity).
8. Which gas in the atmosphere is responsible for the formation of acid rain when it dissolves in
rainwater?
A. Nitrogen
B. Sulfur dioxide
C. Carbon dioxide
D. Argon
CORRECT ANSWER : B
Rationale: Sulfur dioxide reacts with water and oxygen in the atmosphere to form sulfuric acid,
causing acid rain. Nitrogen and Argon are largely inert in this context. Carbon dioxide forms
carbonic acid, which is much weaker than the acids formed by sulfur/nitrogen oxides.
9. Why is potable water treated with chlorine?
A. To remove all dissolved salts.
B. To improve the taste of the water.
C. To kill harmful microbes and bacteria.
D. To soften the water by removing calcium ions.
CORRECT ANSWER : C
Rationale: Chlorine is a powerful disinfectant added to drinking water to destroy pathogens. A,
B, and D describe processes like desalination, filtration, or ion exchange, which are not the
primary purpose of chlorination.
10. A polymer is formed from the monomer $C_3H_6$. What is the structure of the repeating unit?
A. $-[CH_2-CH_2-CH_2]-$
B. $-[CH(CH_3)-CH_2]-$
C. $-[CH_2=CH-CH_3]-$
and Answers/Plus a Rationale Updated 2026 A+/Instant
Download PDF
EXAM COVERAGE
1. Rates of reaction and energy changes
2. Organic chemistry (hydrocarbons, polymers, alcohols, carboxylic acids)
3. Chemical analysis (chromatography, purity, gas identification)
4. Chemistry of the atmosphere (gases, pollutants)
5. Using resources (potable water, corrosion, ceramics, polymers)
1. A student investigates the rate of reaction between marble chips and hydrochloric acid. If 5.0 g
of small marble chips are replaced with 5.0 g of large marble chips while keeping all other
variables constant, what effect does this have on the rate and why?
A. The rate increases because the reaction is more exothermic.
B. The rate decreases because the total surface area of the reactant is smaller.
C. The rate remains the same because the total mass of the reactant is constant.
D. The rate increases because the frequency of successful collisions per second is higher.
CORRECT ANSWER : B
Rationale: Decreasing the size of the marble chips decreases the surface area exposed to the
acid, resulting in fewer collisions per second between reactant particles; therefore, the rate
decreases. A is incorrect because surface area does not change reaction enthalpy. C is incorrect
as rate depends on surface area, not just mass. D is incorrect as the frequency of collisions
decreases, not increases.
2. In the Haber process, the reaction is $N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$ with a
$\Delta H = -92\text{ kJ/mol}$. Which condition set would produce the highest yield of
ammonia at equilibrium?
, A. High pressure and high temperature.
B. Low pressure and low temperature.
C. High pressure and low temperature.
D. Low pressure and high temperature.
CORRECT ANSWER : C
Rationale: According to Le Chatelier's Principle, increasing pressure favors the side with fewer
moles of gas (2 vs 4), and decreasing temperature favors the exothermic direction (forward). A
and D are incorrect because high temperature shifts the equilibrium back to reactants. B is
incorrect because low pressure reduces the yield.
3. Which of the following correctly describes the process of fractional distillation of crude oil?
A. It separates hydrocarbons based on their different melting points.
B. It involves chemical reactions that break down long-chain molecules into smaller ones.
C. It separates a mixture into fractions based on the different boiling points of the hydrocarbons.
D. It produces pure elements from crude oil through electrolysis.
CORRECT ANSWER : C
Rationale: Fractional distillation relies on the physical property of boiling points to separate
crude oil into fractions. A is incorrect because it is based on boiling points, not melting points. B
describes cracking, not distillation. D is incorrect as it is a physical separation, not chemical
synthesis.
4. During the combustion of an alkene, why does the flame appear more smoky or yellow
compared to an alkane of similar length?
A. Alkenes contain a higher percentage of carbon by mass, requiring more oxygen for complete
combustion.
B. Alkenes are more reactive and burn more slowly.
C. Alkenes contain ionic bonds that interfere with the flame.
D. Alkenes always undergo complete combustion.
CORRECT ANSWER : A
, Rationale: Alkenes have a higher carbon-to-hydrogen ratio than alkanes, meaning they require
more oxygen to burn completely; incomplete combustion produces soot (carbon particles). B, C,
and D are factually incorrect regarding combustion characteristics.
5. A student performs paper chromatography to identify food dyes. If a specific dye moves 4.2 cm
and the solvent front moves 7.0 cm, what is the $R_f$ value?
A. 0.60
B. 1.67
C. 0.58
D. 0.70
CORRECT ANSWER : A
Rationale: The $R_f$ value is calculated as the distance moved by the substance divided by the
distance moved by the solvent front ($4.2/7.0 = 0.60$). B, C, and D are mathematical errors in
division.
6. Which property of a hydrocarbon increases as the length of the carbon chain increases?
A. Volatility
B. Flammability
C. Viscosity
D. Rate of evaporation
CORRECT ANSWER : C
Rationale: As chain length increases, intermolecular forces become stronger, making the liquid
more viscous. Volatility, flammability, and rate of evaporation all decrease as chain length
increases.
7. How can the presence of water be confirmed in a chemical sample using a simple chemical test?
A. Add sodium hydroxide and look for a precipitate.
B. Use anhydrous copper(II) sulfate; it will turn from white to blue.
C. Pass the gas through limewater and look for cloudiness.
D. Test the pH using universal indicator.
, CORRECT ANSWER : B
Rationale: Anhydrous copper(II) sulfate is a classic test for water, where the addition of water
causes hydration, changing the color from white to blue. A, C, and D are tests for different
substances (metal ions, $CO_2$, and acidity).
8. Which gas in the atmosphere is responsible for the formation of acid rain when it dissolves in
rainwater?
A. Nitrogen
B. Sulfur dioxide
C. Carbon dioxide
D. Argon
CORRECT ANSWER : B
Rationale: Sulfur dioxide reacts with water and oxygen in the atmosphere to form sulfuric acid,
causing acid rain. Nitrogen and Argon are largely inert in this context. Carbon dioxide forms
carbonic acid, which is much weaker than the acids formed by sulfur/nitrogen oxides.
9. Why is potable water treated with chlorine?
A. To remove all dissolved salts.
B. To improve the taste of the water.
C. To kill harmful microbes and bacteria.
D. To soften the water by removing calcium ions.
CORRECT ANSWER : C
Rationale: Chlorine is a powerful disinfectant added to drinking water to destroy pathogens. A,
B, and D describe processes like desalination, filtration, or ion exchange, which are not the
primary purpose of chlorination.
10. A polymer is formed from the monomer $C_3H_6$. What is the structure of the repeating unit?
A. $-[CH_2-CH_2-CH_2]-$
B. $-[CH(CH_3)-CH_2]-$
C. $-[CH_2=CH-CH_3]-$
