Visual Deduction Past Papers
Topic 3.1.8: Interpreting Chemical Diagrams
Papers 2 & 4 Practice | 15 Questions | 50 Total Marks
📋 EXAM INSTRUCTIONS
- ▸Time Allocation: 60 minutes recommended
- ▸Answer Format: Write answers as you would in the actual exam (formulas, equations, explanations)
- ▸Diagrams: Study each diagram carefully before answering. Count atoms/ions accurately.
- ▸Mark Scheme: Click "Reveal Answer" only after attempting each question
Section A: Molecular Diagrams
1. The diagram shows a ball-and-stick model of an organic molecule.
a) Deduce the molecular formula of this molecule. [2]
b) Name the functional group present. [1]
c) State the type of bonding between carbon and oxygen atoms. [1]
2. The diagram shows the structure of methane.
a) State the molecular formula of methane. [1]
b) Explain why the bond angle in methane is approximately 109.5°. [2]
c) State the type of bonding in methane. [1]
3. A student draws a diagram showing oxygen molecules reacting.
a) Identify the type of bond between the two oxygen atoms in O₂. [1]
b) Explain why this bond is stronger than a single bond. [2]
4. The diagram shows a representation of carbon dioxide at the molecular level.
a) Draw a dot-and-cross diagram for carbon dioxide, showing outer electrons only. [3]
b) State the shape of a carbon dioxide molecule. [1]
5. A diagram shows the structure of ammonia (NH₃).
a) State the number of covalent bonds in one ammonia molecule. [1]
b) Explain why ammonia has a pyramidal shape. [2]
Section B: Ionic Lattices
6. The diagram shows the unit cell structure of cesium chloride.
a) Determine the simplest formula of cesium chloride. [1]
b) Explain how you deduced this formula from the diagram. [2]
c) State the coordination number of the cesium ion. [1]
7. The diagram shows part of the sodium chloride lattice structure.
a) State the formula of sodium chloride. [1]
b) Describe the coordination of ions in this structure. [2]
c) Explain why sodium chloride has a high melting point. [2]
8. A diagram shows the arrangement of ions in magnesium oxide.
a) Compare the melting point of magnesium oxide with sodium chloride. [1]
b) Explain your answer in terms of ionic bonding. [3]
9. The diagram represents the structure of calcium fluoride (CaF₂).
a) State the ratio of calcium ions to fluoride ions in the structure. [1]
b) Explain why this ratio is different from 1:1. [2]
10. A diagram shows the giant ionic lattice of aluminum oxide.
a) Write the formula of aluminum oxide. [1]
b) Explain why aluminum oxide is classified as a giant structure. [2]
Section C: Reactant Ratios
11. The diagram shows the reaction between hydrogen and oxygen to form water.
a) Deduce the balanced equation for this reaction from the diagram. [2]
b) State the number of molecules of water formed from 10 molecules of oxygen. [1]
12. The diagram shows nitrogen reacting with hydrogen to produce ammonia.
a) Write the balanced equation for this reaction. [2]
b) State the mole ratio of nitrogen to hydrogen. [1]
c) Calculate the volume of ammonia produced if 30 cm³ of nitrogen reacts completely. [2]
13. The diagram shows the combustion of methane.
a) Complete the balanced equation: CH₄ + ___ O₂ → ___ CO₂ + ___ H₂O [2]
b) State why the oxygen-to-methane ratio in the diagram is 2:1. [1]
14. A diagram shows the thermal decomposition of calcium carbonate.
a) Write the balanced equation showing this decomposition. [2]
b) State the number of gas molecules produced per formula unit of calcium carbonate. [1]
15. The diagram shows the reaction between carbon monoxide and oxygen.
a) Deduce the balanced equation for this reaction. [2]
b) Explain why this reaction is described as an oxidation reaction. [2]
🎯 VISUAL DEDUCTION EXAM STRATEGY
Molecular Diagrams:
- • Count each atom type carefully
- • Identify functional groups by structure
- • Single line = single bond, double line = double bond
Ionic Lattices:
- • Account for ion sharing (corners, edges, faces)
- • Check coordination numbers carefully
- • Link structure to properties (melting point)
Reactant Ratios:
- • Count molecules on each side
- • Balance using smallest whole numbers
- • Remember: coefficients = mole ratios = volume ratios (for gases)
⚠️ Common Mistakes:
- • Forgetting non-bonding electron pairs
- • Not dividing by sharing factor for lattices
- • Writing unbalanced equations from diagrams
Cambridge IGCSE Chemistry 0620 | 2026-2028 Syllabus
Practice materials designed for visual analysis mastery
Sign In to Keep Going
You've reached the end of the free preview. Sign in — and upgrade to Plus or Pro — to keep going with Chemistry.
Full Access
Unlock all 320 lessons