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*Jun25 7405301* IB/M/Jun25/G4007/V5 7405/3
For Examiner’s Use Question Mark 1 2 3 4 5 6 Section B TOTAL
Friday 20 June 2025 Morning Time allowed: 2 hours
Materials
For this paper you must have:
• the Periodic Table/Data Booklet, provided as an insert (enclosed) • a ruler with millimetre measurements • a scientific calculator, which you are expected to use where appropriate.
Instructions • Use black ink or black ball-point pen.• Fill in the boxes at the top of this page.• Answer all questions.• You must answer the questions in the spaces provided. Do not write outside the box around each page or on blank pages.• If you need extra space for your answer(s), use the lined pages at the end of this book. Write the question number against your answer(s).• All working must be shown.• Do all rough work in this book. Cross through any work you do not want to be marked.
Information • The marks for questions are shown in brackets.• The maximum mark for this paper is 90.
Advice • You are advised to spend 70 minutes on Section A and 50 minutes on Section B.Please write clearly in block capitals.Centre number
Candidate number
Surname
Forename(s)
Candidate signature
I declare this is my own work.A-level
CHEMISTRY
Paper 3 1 / 4
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*02* IB/M/Jun25/7405/3
Do not write outside the box Section A
Answer all questions in this section.
- 1
A value for enthalpy of solution can be determined from the results of a calorimetry experiment or by the application of Hess’s law.
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. 1 Give the equation, including state symbols, for the process that occurs when the enthalpy of solution of potassium hydroxide is determined.[1 mark]
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*03* Turn over ►
IB/M/Jun25/7405/3
Do not write outside the box
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. 2 A student does an experiment to determine a value for the enthalpy of solution of potassium hydroxide.
The student uses this method.
• Add some distilled water to a measuring cylinder and record the volume.• Pour the water into a polystyrene cup.• Record the temperature of the water in the cup.• Add 3.00 g of solid KOH to the water in the cup.• Stir the solution and record the maximum temperature reached.
Table 1 shows the student’s results.
Table 1
Initial temperature / °C 18.1 Final temperature / °C 30.4
The student calculated the enthalpy of solution of potassium hydroxide to be –51.3 kJ mol –1
The specific heat capacity of the solution, c = 4.18 J K –1 g –1
Assume the density of the solution = 1.00 g cm –3
Calculate the volume of water that the student added to the cup.[5 marks]
Volume of water Units
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*04* IB/M/Jun25/7405/3
Do not write outside the box
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. 3 Table 2 shows some enthalpy change data.
Table 2
Enthalpy change / kJ mol –1
Enthalpy of lattice formation of potassium hydroxide
–789
Enthalpy of hydration of potassium ions –322 Enthalpy of hydration of hydroxide ions –528
Use the data in Table 2 to calculate the enthalpy of solution for potassium hydroxide.[2 marks]
Enthalpy of solution
kJ mol –1
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. 4 Suggest why the value calculated in Question 01.3 is different from the experimental value given in Question 01.2.[1 mark]
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