KCSE Chemistry Paper 1 Practice Questions With Answers

The first five questions are free; Learners unlock the rest, the timer and the full review with worked answers.

Dates and times from the KNEC 2026 KCSE timetable.

Paper 1 sweeps the whole Form 1–4 syllabus in small questions, so our paper does too: atomic structure and the periodic table, ionic, covalent and metallic bonding, group trends, acids and salts, separation methods, gas tests, the reactivity series, rates and equilibrium, organic chemistry (alkanes, alkenes and tests), electrolysis, energy changes, the mole, volumetric analysis, gas laws and radioactivity. In the real paper these are written answers; here the concepts are tested with options and the calculations with typed answers, and every item has the reasoning or working a marking scheme would expect.

• Moles: moles = mass ÷ molar mass; use the equation’s ratio; multiply back by molar mass.
• Titration: moles = molarity × volume in dm³ (divide cm³ by 1,000); use the mole ratio; molarity = moles ÷ volume.
• Gas laws: always convert to kelvin (add 273) before using Charles’ or the combined gas law.
• Half-life: count the number of half-lives, then halve that many times.
• Electrolysis: Q = It with time in seconds; 96,500 C is one faraday.
• Heat change: ΔH = mcΔT, then divide by the moles reacting for molar enthalpy, with the sign showing exo- or endothermic.

Paper 1 questions usually carry 1 to 3 marks, and the marks tell you how many points the examiner expects. A 2-mark “explain” question wants a fact and a reason; a 3-mark equation question wants correct formulae, balancing and state symbols. Write equations in full, never in words alone. When asked for an observation, describe what you would see, hear or feel, such as effervescence or a white precipitate, not the name of the product. Keep answers short and precise: long answers waste time and can contradict themselves.

• Using Celsius in gas law calculations.
• Forgetting to convert cm³ to dm³ in titration.
• Writing “the solution changes colour” without stating from what to what. Examiners want both colours.
• Confusing “weak” (partly ionised) with “dilute” (low concentration).
• Saying that the catalyst shifts equilibrium. It only speeds up reaching it.

For the practical, revise reading a burette to two decimal places, averaging consistent titres, and writing observations and inferences in separate columns. More: KCSE Biology practice, KCSE Mathematics practice and the KCSE past papers hub.