5070_s26_ms_21 2026 May-June Chemistry 5070 Mark Scheme 2 Variant 1 · Cambridge CAIE O Level

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5070_s26_ms_212026 May-June Chemistry 5070 Mark Scheme 2 Variant 1

This is the official Cambridge mark scheme for Chemistry (5070) Mark Scheme 2 (Variant 1) from the 2026 May-June session. Mark schemes show exactly how each mark is awarded, including acceptable alternative answers, required key terms, and common errors that lose marks. Cambridge mark schemes use notation like "allow," "accept," and "do not credit" to define the boundary between full marks and zero.

Also referenced as: 5070_s26_ms_21 · 5070/21/m/j/26 ms · 5070/21 May/June 2026 ms

Paper 2: Theory This is Paper 2: Theory, worth 80 marks with a duration of 1h 45m. Structured and free-response questions. Section A: short-answer. Section B: longer structured questions requiring extended writing and calculations.

This mark scheme corresponds to 5070_s26_qp_21. For maximum revision benefit, attempt the question paper under strict exam conditions first, then use this mark scheme to self-assess. Pay attention to the marking notation: "allow" means an alternative is accepted, "do not credit" means a specific phrasing is rejected even if technically correct, and "ORA" (or reverse argument) means the mark can also be earned with the opposite reasoning.

Cambridge mark schemes reward precise language. For Chemistry (5070), look for keywords the examiner requires — definitions must include specific terms (e.g., "per unit mass," "resultant"), and calculations must show working even if the final answer is correct. Understanding mark scheme conventions helps you write answers that hit every marking point, not just the general idea.

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Same paper, other years

Chemistry (5070) Mark Scheme 2 (Variant 1) from other exam sessions — practise the same paper across the years, then check each one against its mark scheme.

Examiner Insights — Paper 2: Theory

Based on analysis of 4 official Cambridge documents (2023, 2024, 2025)

1

Confusing equilibrium with rate of reaction — using collision theory for equilibrium

Candidates confused equilibrium concepts with rate of reaction, often explaining shifts in equilibrium using collision theory rather than Le Chatelier's principle.5070 Paper 2, May/June 2023

How to fix: Rate of reaction = how fast reactants become products (use collision theory). Equilibrium = which direction a reversible reaction shifts (use Le Chatelier's principle). If a question asks about equilibrium position, never mention collision frequency — explain that the system shifts to counteract the change.

2

'Produces a gas' is not an observation — must say effervescence/bubbling

Candidates stated that a gas was produced rather than describing the observable evidence such as effervescence or bubbling.5070 Paper 2, May/June 2023

How to fix: An observation is what you SEE, HEAR, or SMELL. 'A gas is produced' is a conclusion, not an observation. Write 'effervescence/bubbling' instead. Similarly: 'heat is released' should be 'temperature increases' or 'test tube becomes warm to touch'.

3

Drawing organic structures with wrong valencies — missing hydrogens, pentavalent carbon

Many candidates drew organic structures with incorrect valencies, commonly showing carbon with five bonds or omitting hydrogen atoms, resulting in invalid structural formulae.5070 Paper 2, May/June 2023

How to fix: Carbon ALWAYS makes exactly 4 bonds. After drawing a structure, count the bonds on every carbon atom — if any has more or fewer than 4, it is wrong. Add hydrogen atoms to fill any empty bonds. Oxygen = 2 bonds, nitrogen = 3 bonds, hydrogen = 1 bond.

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All Chemistry (5070) Papers — 2026 May-June

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Chemistry Exam Guide: How to Score Higher

Top mistakes, scoring patterns & answer frameworks from 4 official Cambridge documents