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2025 OCR GCSE (9–1) Chemistry B (Twenty First Century Science) J258/04 Depth
in Chemistry (Higher Tier) June QUESTION PAPER and MARK SCHEME
Oxford Cambridge and RSA
Friday 13 June 2025 – Morning
GCSE (9–1) Chemistry B (Twenty First Century Science)
J258/04 Depth in Chemistry (Higher Tier)
Time allowed: 1 hour 45 minutes You must have:
- a ruler (cm/mm)
- the Data Sheet for GCSE (9–1) Chemistry B (inside this document) You can use:
- a scientific or graphical calculator
- an HB pencil
- J 2 5 8 0 4 * Please write clearly in black ink. Do not write in the barcodes. Centre number Candidate number First name(s) Last name INSTRUCTIONS
- Use black ink. You can use an HB pencil, but only for graphs and diagrams.
- Write your answer to each question in the space provided. If you need extra space use the lined pages at the end of this booklet. The question numbers must be clearly shown.
- Answer all the questions.
- Where appropriate, your answer should be supported with working. Marks might be given for using a correct method, even if your answer is wrong. INFORMATION
- The total mark for this paper is 90.
- The marks for each question are shown in brackets [ ].
- Quality of extended response will be assessed in questions marked with an asterisk (*).
- This document has 32 pages. ADVICE
- Read each question carefully before you start your answer.
H
© OCR 2025 [601/8605/7] DC (SL/FC) 354030/ OCR is an exempt Charity Turn over
(^1) (^8) (^9) (^4) (^1) (^5) (^5) (^5) (^9) (^7) (^) *
© OCR 2025
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© OCR 2025 Turn over 1 Potassium, sodium and lithium are metals in Group 1 of the Periodic Table. A student watches a video of the reaction of potassium with water. Fig. 1.1 shows a diagram of the experiment. Fig. 1. Water (^) Potassium The table shows information about this reaction. Metal Products of the reaction Observations Potassium Potassium hydroxide Hydrogen gas Potassium moves quickly on the surface of the water and fizzes violently. Potassium burns with a pale purple flame. (a) The student then watches a video of the reaction of sodium with water. Predict the products of the reaction of sodium with water and describe the observations you expect. Products ................................................................. and ................................................................. Observations .................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... [3]
© OCR 2025 Turn over Li F (iii) Lithium fluoride is an ionic compound that has lithium ions and fluoride ions. Fig. 1.3 shows a dot and cross diagram of these ions. The diagram is not complete. Fig. 1. ........ ........ Complete Fig. 1.. You need to:
- show the arrangement of electrons in the fluoride ion
- show the charges on both ions. [3] (iv) Which statement gives a correct limitation of using a complete dot and cross diagram to represent ionic bonding? Tick (✓) one box. It does not show that the ions are different sizes. It does not show the correct ratio of numbers of ions. It does not show the total number of electrons. It only shows shared electrons. [1]
© OCR 2025 2 A student does an electrolysis experiment.
They pass electricity through dilute aqueous copper(II) sulfate using inert electrodes.
The diagram shows the apparatus they set up. Negative electrode Positive electrode Dilute aqueous
copper(II) sulfate
To power supply (a) Oxygen gas forms at the positive electrode. Which two statements give correct reasons why oxygen forms at the positive electrode? Tick (✓) two boxes. Copper reacts with water to form oxygen. Hydroxide ions from water react to form oxygen. Non-metals usually form at the positive electrode. The electricity causes water to evaporate around the electrode. [2]
© OCR 2025 Heat Pure water Sea water Water in Water out ............................. 3 Water for drinking can be separated from sea water by distillation. (a) The diagram shows a laboratory apparatus that can be used for the distillation of sea water. (i) Complete the labels on the diagram. Use all of the words from the list. [2]
© OCR 2025 Turn over (ii) Sea water contains dissolved sodium chloride. A student adds dilute acidified silver nitrate to the sea water before distillation and to the water collected after distillation. Complete the table to show the observations that the student makes. Explain your answer. Observations when acidified silver nitrate is added Sea water before distillation Water collected after distillation Explanation ...................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... [3]
© OCR 2025 Turn over (ii) Some people think that chlorine should not be added to drinking water because it causes other health issues such as allergies in some people. Suggest why chlorine should be added to drinking water. Include in your answer:
- ideas about risk and benefit
- data from the graph. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... . ................................................................................................................................................. [3] (c) The effect of adding chlorine to drinking water was an important scientific discovery. Today, information about important scientific discoveries is published for peer review. Information about important scientific discoveries is also published in newspapers. Explain the differences between publishing information for peer review and in newspapers. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... . ................................................................................................................................................. [3]
© OCR 2025 4 Pure iron corrodes easily and is too weak for some uses.
(a) When iron corrodes it reacts with oxygen to make iron(III) oxide.
Complete the balanced symbol equation for the reaction. Include state symbols.
iron + oxygen iron(III) oxide
......... (....) + ............... (....) 2Fe 2 O 3 (....) [3] (b) Steel is a mixture of iron and other elements. Table 4.1 shows the effect of different elements on the properties of steel. Table 4. Element Effect on properties of steel Percentage in steel Chromium Increases corrosion resistance, especially at high temperatures.
Nickel Increases corrosion resistance and can be bent without breaking.
Carbon Increases hardness but also makes steel more easy to break. No effect on corrosion resistance.
Copper Increases electrical conductivity. Increases corrosion resistance in sea water.
Manganese Increases hardness but can make steel more easy to break when bent.
(i) A type of steel contains 2% carbon and 98% iron. Explain why this steel has a limited range of uses. Use Table 4.1 to help you answer. .......................................................................................................................................................... .......................................................................................................................................................... ..........................................................................................................................................................
. ................................................................................................................................................. [2]
© OCR 2025 5 Nitrogen and hydrogen react together to make ammonia in the Haber process. Ammonia is used in fertilisers. (a) Which statements about fertilisers are true and which are false? Tick (✓) one box in each row. [2] True False Ammonia is added to fertilisers to provide potassium and phosphorus for plant growth. Fertilisers made from ammonia are needed to balance supply and demand of food. Industrial processes used to make fertilisers are usually on a large scale in batches.
© OCR 2025 **Turn over (b) *** The diagram shows a flow chart for the substances that enter and leave the reactor in the Haber process. The table shows the main conditions used. Nitrogen and hydrogen Unreacted gases recycled Mixture of gases Ammonia Explain why the conditions in the table are chosen for this process. Include in your answer:
- the effect each condition has on the rate of reaction and on the yield
- why higher or lower values of temperature and pressure are not used. .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... .......................................................................................................................................................... . ................................................................................................................................................. [6]
450 °C
200 atm catalyst unreacted gases recycled Conditions used Reactor
© OCR 2025 Turn over (c) Table 6.1 shows the relative formula masses for the reactants and products in the reaction of methane with steam. Table 6. Relative formula mass CH 4 16 H 2 O 18 H 2 2 CO 2 ........................................... (i) Complete Table 6.1 by calculating the relative formula mass for carbon dioxide. Use the Periodic Table. [1] (ii) Calculate the atom economy of the reaction of methane with steam to make hydrogen. Use:
- Equation^1 : CH 4 +^ 2H 2 O^ 4H 2 +^ CO 2
- the data from Table 6.. Give your answer to 1 decimal place. Atom economy =....................................................... % [4]
© OCR 2025 (d) Scientists did some experiments and collected data about the yield of the products made when 1000 kg of methane reacts with steam. Table 6.2 shows the data they collected. Table 6. Mass of methane used (kg) 1000 Theoretical yield of hydrogen (kg) 500 Actual mass of hydrogen formed (kg) 370 Actual mass of carbon dioxide formed (kg) 2035 Calculate the percentage yield of hydrogen. Use data from Table 6.. Percentage yield of hydrogen = ....................................................... % [2] (e) Methanol can be made by reacting carbon dioxide with hydrogen. Equation 2 shows this reaction. Equation 2 CO 2 + 3H 2 CH 3 OH + H 2 O (i) Explain how Equation 2 shows that the percentage yield of methanol is not 100%. .......................................................................................................................................................... .......................................................................................................................................................... ..........................................................................................................................................................
. ................................................................................................................................................. [2] (ii) Explain how Equation 2 shows that the atom economy of the reaction to make methanol is not 100%. .......................................................................................................................................................... . ................................................................................................................................................. [1]
