AS LEVEL CHEMISTRY B (SALTERS): Actual May 2025 PAST PAPER 2: Chemistry
in depth. All Assessment Questions & Mark Scheme [OCR H033/02]
Exam Resource Summary
The AS Level Chemistry B (Salters) May 2025 Paper 2: Chemistry in Depth (OCR H033/02)
– All Assessment Questions & Mark Scheme integrates the complete official examination paper
with its full mark scheme, providing a comprehensive and practical tool for exam preparation.
This paper assesses students’ ability to apply and extend their understanding of core chemical
principles to more complex and contextualised problems. Key topics include energetics, kinetics,
equilibria, redox chemistry, organic synthesis, spectroscopy, and the chemistry of materials.
It also examines data analysis, experimental techniques, and the integration of chemical concepts
across different areas of study. The merged format presents each question alongside its
corresponding marking criteria, giving students clear insight into examiner expectations, mark
allocation, and effective problem-solving approaches. This resource is essential for targeted
revision, self-assessment, and the strengthening of analytical and evaluative skills, ensuring
confident preparation for the May 2026 OCR AS Level Chemistry B (Salters) Paper 2 and a
solid grounding for further chemical studies.
Turn over
, 2
1 Catalytic converters on cars use metals such as platinum as heterogeneous catalysts.
Catalytic converters turn exhaust emissions such as carbon monoxide and nitrogen monoxide
into less hazardous products.
(a)
(i) Explain the meaning of the term heterogeneous here.
..........................................................................................................................................................
. ................................................................................................................................................. [1]
(ii) Why is carbon monoxide hazardous?
..........................................................................................................................................................
. ................................................................................................................................................. [1]
(iii) Write an equation for the reaction of carbon monoxide with nitrogen monoxide to give less
hazardous products.
[1]
(iv) A simple model to explain the function of a heterogeneous catalyst involves four steps.
Complete Step 2 and Step 3 in the sequence below.
Step 1 Reactants are adsorbed onto the surface of the catalyst.
Step 2 ...........................................................................................................................................
Step 3 ...........................................................................................................................................
Step 4 Products are desorbed from the surface of the catalyst.
[1]
© OCR 2025
, 3
(b)* Explain how a catalyst increases the rate of a reaction.
Draw an energy profile and a Boltzmann distribution.
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Extra answer space if required.
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© OCR 2025 Turn over
, 4
2 Ethanol is an important alcohol that is made industrially by the hydration of ethene.
(a) Give the conditions required for this industrial process.
..........................................................................................................................................................
..........................................................................................................................................................
. ................................................................................................................................................. [2]
(b) Ethanol can also be made in the laboratory by a two-step process as shown:
CH2=CH2 + H2SO4 CH3CH2OSO3H Step 1
CH3CH2OSO3H + H2O CH3CH2OH + H2SO4 Step 2
Write the overall equation for this two-step process.
[1]
(c) A student does the two-step process in part (b) using an alkene that is a liquid at room
temperature. The reaction is exothermic.
(i) The alkene has a boiling point of 30 °C and is highly flammable.
Suggest a practical arrangement that the student should use to avoid loss of the alkene as a
vapour.
..........................................................................................................................................................
. ................................................................................................................................................. [1]
(ii) When the student has carried out both steps, a mixture is left. This mixture contains an alcohol.
The student finds that drops of this mixture turn bromine water from brown to colourless.
Suggest what this colour change tells the student about the conversion of the alkene into alcohol.
..........................................................................................................................................................
. ................................................................................................................................................. [1]
© OCR 2025
in depth. All Assessment Questions & Mark Scheme [OCR H033/02]
Exam Resource Summary
The AS Level Chemistry B (Salters) May 2025 Paper 2: Chemistry in Depth (OCR H033/02)
– All Assessment Questions & Mark Scheme integrates the complete official examination paper
with its full mark scheme, providing a comprehensive and practical tool for exam preparation.
This paper assesses students’ ability to apply and extend their understanding of core chemical
principles to more complex and contextualised problems. Key topics include energetics, kinetics,
equilibria, redox chemistry, organic synthesis, spectroscopy, and the chemistry of materials.
It also examines data analysis, experimental techniques, and the integration of chemical concepts
across different areas of study. The merged format presents each question alongside its
corresponding marking criteria, giving students clear insight into examiner expectations, mark
allocation, and effective problem-solving approaches. This resource is essential for targeted
revision, self-assessment, and the strengthening of analytical and evaluative skills, ensuring
confident preparation for the May 2026 OCR AS Level Chemistry B (Salters) Paper 2 and a
solid grounding for further chemical studies.
Turn over
, 2
1 Catalytic converters on cars use metals such as platinum as heterogeneous catalysts.
Catalytic converters turn exhaust emissions such as carbon monoxide and nitrogen monoxide
into less hazardous products.
(a)
(i) Explain the meaning of the term heterogeneous here.
..........................................................................................................................................................
. ................................................................................................................................................. [1]
(ii) Why is carbon monoxide hazardous?
..........................................................................................................................................................
. ................................................................................................................................................. [1]
(iii) Write an equation for the reaction of carbon monoxide with nitrogen monoxide to give less
hazardous products.
[1]
(iv) A simple model to explain the function of a heterogeneous catalyst involves four steps.
Complete Step 2 and Step 3 in the sequence below.
Step 1 Reactants are adsorbed onto the surface of the catalyst.
Step 2 ...........................................................................................................................................
Step 3 ...........................................................................................................................................
Step 4 Products are desorbed from the surface of the catalyst.
[1]
© OCR 2025
, 3
(b)* Explain how a catalyst increases the rate of a reaction.
Draw an energy profile and a Boltzmann distribution.
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
. ................................................................................................................................................. [6]
Extra answer space if required.
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
© OCR 2025 Turn over
, 4
2 Ethanol is an important alcohol that is made industrially by the hydration of ethene.
(a) Give the conditions required for this industrial process.
..........................................................................................................................................................
..........................................................................................................................................................
. ................................................................................................................................................. [2]
(b) Ethanol can also be made in the laboratory by a two-step process as shown:
CH2=CH2 + H2SO4 CH3CH2OSO3H Step 1
CH3CH2OSO3H + H2O CH3CH2OH + H2SO4 Step 2
Write the overall equation for this two-step process.
[1]
(c) A student does the two-step process in part (b) using an alkene that is a liquid at room
temperature. The reaction is exothermic.
(i) The alkene has a boiling point of 30 °C and is highly flammable.
Suggest a practical arrangement that the student should use to avoid loss of the alkene as a
vapour.
..........................................................................................................................................................
. ................................................................................................................................................. [1]
(ii) When the student has carried out both steps, a mixture is left. This mixture contains an alcohol.
The student finds that drops of this mixture turn bromine water from brown to colourless.
Suggest what this colour change tells the student about the conversion of the alkene into alcohol.
..........................................................................................................................................................
. ................................................................................................................................................. [1]
© OCR 2025
