KCSE Chemistry Paper 2 (233/2) Questions and Answers

Updated 1 November 2026. These KCSE Chemistry Paper 2 questions and answers are original structured questions in the 233/2 style, with full working for every calculation and the marking points for every explanation. Paper 2 is the long-question theory paper, and the 2026 sitting is on Wednesday 4 November, 8.00 to 10.00 am, according to the KNEC 2026 KCSE Examination Timetable. Nothing here is a KNEC paper or a KNEC marking scheme.

How Chemistry Paper 2 Differs From Paper 1

Paper 2 lasts 2 hours and carries 80 marks, like Paper 1, but instead of 25 to 30 short items it has about seven longer structured questions, each worth roughly 10 to 13 marks and all compulsory. Each question follows one theme from start to finish, such as a flow chart of an industrial process or a series of organic reactions, so one early mistake can cost later parts. Read the whole question before you write.

The subject is worth the effort: Chemistry was one of 17 subjects that recorded a significant improvement in the 2024 KCSE, according to the Education Cabinet Secretary’s statement as reported in the People Daily report on 2024 KCSE subject performance.

KCSE Chemistry Paper 2 Questions and Answers (Original Practice)

Question 1: Organic chemistry (10 marks)

(a) Name CH₃CH₂CH₂OH and give its functional group. (2) (b) Write an equation for the reaction of ethanoic acid with ethanol and name the product. (2) (c) State the conditions for the reaction in (b). (2) (d) Give two differences between soapy and soapless detergents. (2) (e) Name the type of polymerisation that produces polyethene. (2)

Worked answer: (a) Propan-1-ol; hydroxyl group (–OH). (b) CH₃COOH + CH₃CH₂OH ⇌ CH₃COOCH₂CH₃ + H₂O; ethyl ethanoate. (c) Concentrated sulphuric acid as catalyst; warming. (d) Soapless detergents do not form scum with hard water, soapy ones do; soapless detergents are made from petroleum products, soapy ones from fats and oils. (e) Addition polymerisation.

Question 2: Electrolysis (9 marks)

Dilute copper(II) sulphate is electrolysed with copper electrodes. A current of 2 A flows for 32 minutes 10 seconds. (a) Write the equation at the cathode. (1) (b) State what happens to the anode. (1) (c) Calculate the mass of copper deposited. (Cu = 63.5, 1 Faraday = 96,500 C) (4) (d) Explain why the colour of the electrolyte stays the same. (3)

Worked answer: (a) Cu²⁺(aq) + 2e⁻ → Cu(s). (b) It dissolves and becomes thinner. (c) Time = 1,930 s; Q = It = 2 × 1,930 = 3,860 C. 2 × 96,500 C deposit 63.5 g, so 3,860 C deposit 63.5 × 3,860 ÷ 193,000 = 1.27 g. (d) For every Cu²⁺ ion discharged at the cathode, a copper atom at the anode ionises to Cu²⁺, so the concentration of blue Cu²⁺ ions in solution does not change.

Question 3: Energy changes (8 marks)

50 cm³ of 2 M HCl was mixed with 50 cm³ of 2 M NaOH. The temperature rose from 22.0 °C to 35.5 °C. (Specific heat capacity 4.2 J g⁻¹ K⁻¹, density 1 g cm⁻³) (a) Calculate the heat evolved. (2) (b) Calculate the molar enthalpy of neutralisation. (3) (c) Explain why the value for ethanoic acid would be lower. (3)

Worked answer: (a) ΔH = mcΔT = 100 × 4.2 × 13.5 = 5,670 J. (b) Moles of water formed = 2 × 50 ÷ 1000 = 0.1 mol; molar enthalpy = −5,670 ÷ 0.1 = −56,700 J mol⁻¹ = −56.7 kJ mol⁻¹ (the negative sign earns a mark). (c) Ethanoic acid is a weak acid that is only partly ionised; some of the heat released is used to ionise it fully, so less heat is given out.

Question 4: Industrial chemistry (6 marks)

(a) Name the catalyst used in the Haber process. (1) (b) Explain why a temperature of about 450 °C is used even though the forward reaction is exothermic. (3) (c) Give two uses of ammonia. (2)

Worked answer: (a) Finely divided iron. (b) A lower temperature would give a higher yield but the reaction would be too slow; about 450 °C gives an acceptable yield at an economic rate (the optimum temperature). (c) Manufacture of nitrogenous fertilisers; making nitric acid; refrigerant. Any two.

Marks Candidates Throw Away in Paper 2

• Leaving out the negative sign on exothermic enthalpy values.
• Drawing graphs without labelled axes, units or a sensible scale.
• Naming organic compounds by common names when IUPAC names are asked.
• Explaining Le Chatelier’s principle without saying which way the equilibrium shifts.

Time Plan for 2 Hours

Spend 5 minutes reading, then about 14 minutes per question for seven questions, leaving 15 minutes to check units and signs. KNEC instructions say reading time is part of the time shown on the paper, so start the clock from the moment you open it.

More Chemistry Revision

Read the KCSE Chemistry Paper 2 revision guide for topic notes, then race the clock in the Chemistry Paper 2 challenge and the KCSE Chemistry quiz. Paper 1 practice is in KCSE 2025 Chemistry Paper 1 questions and answers, and all chemistry papers are listed on KCSE Chemistry practice papers. See also the KCSE quiz list and the KCSE hub.

Frequently Asked Questions

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