Chemical Reactions | Practice Tests | Chemistry | Form 2 | CBC

KASEMPA DAY

SCIENCE DEPARTMENT

FORM: 2 TERM: 2 YEAR: 2026

TIME: 1 HOUR 30 MINUTES TOTAL MARKS: 50

NAME OF PUPIL: ...............................................................................................

SUBJECT: CHEMISTRY

INSTRUCTIONS:

1. Answer ALL questions in the spaces provided.

2. Show all working for calculations.

3. Use correct units where applicable.

4. Marks for each question are shown in brackets.

═════════════════════════════════════════════════════════

SECTION A 1. In the school laboratory a learner pours 50 cm³ of vinegar (dilute ethanoic acid) into a test-tube and then adds a small spoon of baking soda (sodium hydrogen carbonate). The mixture foams and a balloon fitted over the tube inflates. (a) Describe the observable chemical changes that show a chemical reaction has occurred. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... (b) Write the balanced chemical equation for the reaction, using correct chemical formulae and state symbols in lower case. [3] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... (c) Give one safety precaution the learner should follow during this activity. [1] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 2. A mason heats limestone (a rock mainly of calcium carbonate) to make quicklime for building. When heated strongly the limestone breaks down to a solid and a gas. (a) Identify the type of reaction taking place and explain why it is that type. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... (b) Write the balanced chemical equation for the thermal decomposition, using state symbols. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... (c) State one common use of the solid product formed. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 3. A group of learners place clean iron nails into a blue solution of copper(II) sulfate. After some time the blue colour fades and brown solid forms on the nails. (a) Explain the observations and name the type of reaction. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... (b) Write a balanced chemical equation for the reaction using correct formulae and state symbols. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 4. In an experiment two clear solutions are mixed and a white solid settles out of the mixture. A teacher tells the class this is a precipitation reaction. (a) From this situation construct the balanced molecular equation for mixing aqueous sodium chloride and aqueous silver nitrate to form aqueous sodium nitrate and a white precipitate of silver chloride. Include state symbols. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... (b) Write the ionic equation and then the net ionic equation showing only the species that change. Use appropriate ionic charges. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... SECTION B 1. During a power cut a family lights a paraffin lantern. The teacher explains that burning paraffin is a chain reaction at molecular level. (a) Using the lantern as context, describe what is meant by a chain reaction in simple terms. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... (b) Give one balanced chemical equation for complete combustion of a hydrocarbon such as paraffin (use general formula C_xH_y or methane for simplicity) and describe briefly the steps named initiation, propagation and termination in this chain-type process. [4] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 2. A student collects a small sample of hydrogen gas and burns it carefully at the lab sink showing water forms on a cold surface nearby. (a) Identify the type of reaction and give one reason from the observation that supports your choice. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... (b) Write the balanced chemical equation for the formation of water from hydrogen and oxygen including correct state symbols. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... (c) Suggest two safety precautions the student must follow when preparing and burning hydrogen gas in the school lab. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 3. A learner mixes aqueous lead(II) nitrate with aqueous potassium iodide during a demonstration. A yellow precipitate forms. (a) Write a balanced molecular equation (with state symbols) for this reaction. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... (b) Write the ionic equation and then the net ionic equation for the formation of the yellow precipitate. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... SECTION C 1. A teacher asks you to plan a short experiment to show that magnesium ribbon reacts with dilute hydrochloric acid producing a gas. (a) List the apparatus and reagents you would need. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... (b) Describe the step-by-step procedure the learner should follow and the observations that show a chemical reaction has happened. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... (c) Write the word equation and the balanced chemical equation (with state symbols) for the reaction between magnesium and dilute hydrochloric acid. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 2. On a farm a metal plate left in the sun turns shiny at first and then forms a white coating as it reacts with oxygen in air. (a) From this description write a word equation for a metal combining with oxygen to form a metal oxide. [1] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... (b) Give an example using aluminium and write the balanced chemical equation for its reaction with oxygen (direct combination). Include state symbols. [3] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... 3. A clinic assistant observes that mixing small amounts of hydrochloric acid and sodium hydroxide solutions produces neutral salt water. (a) From the clinic example write the balanced chemical equation with state symbols for the neutralisation reaction. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... (b) Write the ionic equation and then the net ionic equation for this neutralisation. [2] .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... .......................................................................................................................................................................... ..........................................................................................................................................................................

test — Chemistry (Chemical Reactions)

Want to create your own resources?