A LEVEL CHEMISTRY B (SALTERS): Actual June 2025 PAST PAPER 2:
Scientific literacy in chemistry. All Assessment Questions & Mark Scheme [OCR
H433/02]
Exam Resource Summary
The A Level Chemistry B (Salters) June 2025 Paper 2: Scientific Literacy in Chemistry
(OCR H433/02) – All Assessment Questions & Mark Scheme combines the complete official
examination paper with its detailed mark scheme, offering a comprehensive and structured
resource for advanced exam preparation. This paper assesses students’ ability to apply chemical
knowledge to real-world contexts, demonstrating scientific literacy, data interpretation,
critical analysis, and evaluative reasoning. Key areas of focus include energy changes,
kinetics, equilibria, organic and inorganic chemistry, spectroscopy, and the social and
environmental applications of chemistry. Students are expected to analyse unfamiliar
information, evaluate evidence, and construct well-reasoned arguments grounded in scientific
principles. The merged format aligns each question with its marking criteria, providing clear
insight into examiner expectations, mark allocation, and effective response strategies. This
resource is essential for focused revision, self-assessment, and the development of higher-
order analytical and evaluative skills, ensuring confident preparation for the June 2026 OCR A
Level Chemistry B (Salters) Paper 2 and future scientific study or research
Turn over
, 2
1 This question is about reactions of haloalkanes.
(a) CH3Cl is made by plants that grow on marshes.
If CH3Cl reaches the stratosphere, electromagnetic radiation causes it to undergo homolytic
fission forming chlorine radicals.
(i) Give the systematic name of CH3Cl .
. ................................................................................................................................................. [1]
(ii) Draw ‘half curly arrows’ to show the mechanism of the homolytic fission of CH3Cl .
Show the products of the reaction.
H
H C Cl
H
[2]
(iii) Which type of electromagnetic radiation causes this homolytic fission to occur in the stratosphere?
. ................................................................................................................................................. [1]
(iv) The bond energy of the C–Cl bond is 346 kJ mol–1.
Calculate the wavelength (in m) of radiation which breaks this bond.
Give your answer to an appropriate number of significant figures.
Wavelength = ..................................................... m [5]
(v) Chlorine radicals catalyse the breakdown of ozone in the stratosphere.
Write equations to show how this occurs and give the overall equation.
Overall equation:
[2]
© OCR 2025
, 3
(vi) Why is the breakdown of ozone in the stratosphere harmful to humans?
..........................................................................................................................................................
..........................................................................................................................................................
. ................................................................................................................................................. [2]
(b) CH3Cl reacts with ammonia to give an amine salt.
CH3Cl + NH3 CH3NH3Cl Equation 1.1
Ammonia is acting as a nucleophile here.
(i) Explain what is meant by the term nucleophile.
..........................................................................................................................................................
. ................................................................................................................................................. [1]
(ii) Show the mechanism of Equation 1.1.
Use curly arrows and show relevant lone pairs and the ionic products.
H
H C Cl
H
H N H
H
[2]
(iii) The product of Equation 1.1 is a salt of CH3NH2.
Give the systematic name for CH3NH2.
. ................................................................................................................................................. [1]
(c) The reaction between a haloalkane and hydroxide ions is a nucleophilic substitution reaction.
A student reacts 1-chlorobutane, 1-bromobutane and 1-iodobutane separately with aqueous
sodium hydroxide.
Which will react fastest and why?
..........................................................................................................................................................
..........................................................................................................................................................
. ................................................................................................................................................. [2]
© OCR 2025 Turn over
, 4
2 Some students study the nitrogen compounds in the soil.
(a) How many neutrons are in an atom of 14N?
. ................................................................................................................................................. [1]
(b) The students make ammonia from a fertiliser containing NH4+ ions.
Identify the reagent that they use.
. ................................................................................................................................................. [1]
(c) The students add an aqueous solution of ammonia to a solution of FeSO4.
A precipitate forms.
Give the colour of the precipitate and write an ionic equation for its formation.
Include state symbols.
Colour: ..............................................................................................................................................
Ionic equation:
[3]
(d) The students read that ammonium ions are oxidised to NO2– by bacteria in the soil.
(i) Give the systematic name of NO2–.
. ................................................................................................................................................. [1]
(ii) The students add acid to NaNO2(s) in a test tube.
A colourless gas A (with nitrogen in the +2 oxidation state) and NO 3– ions are produced.
Gas A turns to a brown gas B at the top of the test tube.
Suggest the formula of the brown gas B.
Suggest an ionic equation for the formation of gas A from acidified NO 2– ions.
Formula of brown gas B: ..................................................................................................................
Ionic equation:
[3]
© OCR 2025
Scientific literacy in chemistry. All Assessment Questions & Mark Scheme [OCR
H433/02]
Exam Resource Summary
The A Level Chemistry B (Salters) June 2025 Paper 2: Scientific Literacy in Chemistry
(OCR H433/02) – All Assessment Questions & Mark Scheme combines the complete official
examination paper with its detailed mark scheme, offering a comprehensive and structured
resource for advanced exam preparation. This paper assesses students’ ability to apply chemical
knowledge to real-world contexts, demonstrating scientific literacy, data interpretation,
critical analysis, and evaluative reasoning. Key areas of focus include energy changes,
kinetics, equilibria, organic and inorganic chemistry, spectroscopy, and the social and
environmental applications of chemistry. Students are expected to analyse unfamiliar
information, evaluate evidence, and construct well-reasoned arguments grounded in scientific
principles. The merged format aligns each question with its marking criteria, providing clear
insight into examiner expectations, mark allocation, and effective response strategies. This
resource is essential for focused revision, self-assessment, and the development of higher-
order analytical and evaluative skills, ensuring confident preparation for the June 2026 OCR A
Level Chemistry B (Salters) Paper 2 and future scientific study or research
Turn over
, 2
1 This question is about reactions of haloalkanes.
(a) CH3Cl is made by plants that grow on marshes.
If CH3Cl reaches the stratosphere, electromagnetic radiation causes it to undergo homolytic
fission forming chlorine radicals.
(i) Give the systematic name of CH3Cl .
. ................................................................................................................................................. [1]
(ii) Draw ‘half curly arrows’ to show the mechanism of the homolytic fission of CH3Cl .
Show the products of the reaction.
H
H C Cl
H
[2]
(iii) Which type of electromagnetic radiation causes this homolytic fission to occur in the stratosphere?
. ................................................................................................................................................. [1]
(iv) The bond energy of the C–Cl bond is 346 kJ mol–1.
Calculate the wavelength (in m) of radiation which breaks this bond.
Give your answer to an appropriate number of significant figures.
Wavelength = ..................................................... m [5]
(v) Chlorine radicals catalyse the breakdown of ozone in the stratosphere.
Write equations to show how this occurs and give the overall equation.
Overall equation:
[2]
© OCR 2025
, 3
(vi) Why is the breakdown of ozone in the stratosphere harmful to humans?
..........................................................................................................................................................
..........................................................................................................................................................
. ................................................................................................................................................. [2]
(b) CH3Cl reacts with ammonia to give an amine salt.
CH3Cl + NH3 CH3NH3Cl Equation 1.1
Ammonia is acting as a nucleophile here.
(i) Explain what is meant by the term nucleophile.
..........................................................................................................................................................
. ................................................................................................................................................. [1]
(ii) Show the mechanism of Equation 1.1.
Use curly arrows and show relevant lone pairs and the ionic products.
H
H C Cl
H
H N H
H
[2]
(iii) The product of Equation 1.1 is a salt of CH3NH2.
Give the systematic name for CH3NH2.
. ................................................................................................................................................. [1]
(c) The reaction between a haloalkane and hydroxide ions is a nucleophilic substitution reaction.
A student reacts 1-chlorobutane, 1-bromobutane and 1-iodobutane separately with aqueous
sodium hydroxide.
Which will react fastest and why?
..........................................................................................................................................................
..........................................................................................................................................................
. ................................................................................................................................................. [2]
© OCR 2025 Turn over
, 4
2 Some students study the nitrogen compounds in the soil.
(a) How many neutrons are in an atom of 14N?
. ................................................................................................................................................. [1]
(b) The students make ammonia from a fertiliser containing NH4+ ions.
Identify the reagent that they use.
. ................................................................................................................................................. [1]
(c) The students add an aqueous solution of ammonia to a solution of FeSO4.
A precipitate forms.
Give the colour of the precipitate and write an ionic equation for its formation.
Include state symbols.
Colour: ..............................................................................................................................................
Ionic equation:
[3]
(d) The students read that ammonium ions are oxidised to NO2– by bacteria in the soil.
(i) Give the systematic name of NO2–.
. ................................................................................................................................................. [1]
(ii) The students add acid to NaNO2(s) in a test tube.
A colourless gas A (with nitrogen in the +2 oxidation state) and NO 3– ions are produced.
Gas A turns to a brown gas B at the top of the test tube.
Suggest the formula of the brown gas B.
Suggest an ionic equation for the formation of gas A from acidified NO 2– ions.
Formula of brown gas B: ..................................................................................................................
Ionic equation:
[3]
© OCR 2025
