Attempt rules

• Time: 30 minutes writing + 8 minutes checking.
• Maximum marks: 30.
• Use blank paper and a pen.
• Keep notes, the chapter pack and answer reveals closed.
• Attempt every question before opening the answer check.
• The questions are original board-style practice. They are not predictions or previous-year questions.

Question paper

Section A - Objective questions - 9 marks

Choose the correct answer. Questions 7-9 are Assertion-Reason questions.

1. Which equation is correctly balanced? (1)

1. H₂ + O₂ → H₂O
2. 2H₂ + O₂ → 2H₂O
3. H₂ + 2O₂ → H₂O
4. 2H₂ + 2O₂ → H₂O

1. The brown fumes produced by heating lead nitrate are mainly: (1)

1. oxygen
2. nitrogen dioxide
3. sulphur dioxide
4. hydrogen

1. Which reaction is both double displacement and precipitation? (1)

1. CaO + H₂O → Ca(OH)₂
2. Fe + CuSO₄ → FeSO₄ + Cu
3. Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl
4. 2AgCl → 2Ag + Cl₂

1. During electrolysis of water, the volume ratio H₂:O₂ is: (1)

1. 1:1
2. 1:2
3. 2:1
4. 4:1

1. In CuO + H₂ → Cu + H₂O, the reducing agent is: (1)

1. CuO
2. H₂
3. Cu
4. H₂O

1. Nitrogen flushing delays rancidity because it: (1)

1. increases the packet temperature
2. adds water to the food
3. limits contact between fats and oxygen
4. converts fats into proteins

For Questions 7-9 choose:

1. Both A and R are true, and R correctly explains A.
2. Both A and R are true, but R does not correctly explain A.
3. A is true, but R is false.
4. A is false, but R is true.

1. Assertion: A balanced equation obeys conservation of mass. Reason: The number of atoms of each element is equal on both sides. (1)

1. Assertion: Silver chloride turns grey in sunlight. Reason: Silver chloride combines with chlorine to form a grey compound. (1)

1. Assertion: CaO + H₂O → Ca(OH)₂ is a combination reaction. Reason: Two reactants form one product. (1)

Section B - Very short answers - 6 marks

1. Why must a magnesium ribbon be cleaned before burning? Write the balanced equation for its burning. (2)

1. State two differences between displacement and double displacement reactions. (2)

1. Why is respiration exothermic? Write the equation used in this chapter. (2)

Section C - Short answers - 6 marks

1. Green ferrous sulphate crystals are heated strongly. State two observations, name the reaction type and write the balanced decomposition equation. (3)

1. A student mixes lead nitrate and potassium iodide solutions. Write the observation and balanced equation. Explain why the reaction has two valid classifications. (3)

Section D - Long answer - 5 marks

1. Compare thermal, electrolytic and photochemical decomposition. For each, name the energy supplied and write one balanced equation. Finish by explaining why all three are decomposition reactions. (5)

Section E - Case-based question - 4 marks

1. Three unlabeled stations show the following results:

• Station P becomes warm when water is added to a white solid.
• Station Q changes from a blue solution to a pale-green solution when an iron nail is added.
• Station R contains an oily food sample that develops an unpleasant smell after long exposure to air.

(a) Name the white solid at Station P. (1)

(b) Classify the reaction at Station P. (1)

(c) Write the balanced equation for Station Q. (1)

(d) Name the process at Station R and state one way to slow it. (1)

Final eight-minute check

Use this order:

1. Did I answer every subpart?
2. Did I balance every equation?
3. Did I add states and conditions where known?
4. Did I include the observation and the reason?
5. Did I label question numbers clearly?

Score profile

Also record the first failed skill: balancing, observation, equation, classification, reason, redox agent, or multi-part completion. The first failed skill is more useful than the total alone.