2024 Cambridge IGCSE Chemistry (0620) Practice Paper with Answers

A student investigates the reaction between dilute hydrochloric acid and a large excess of calcium carbonate (marble chips). The temperature of the mixture is increased from 20 °C to 30 °C. All other conditions remain constant. Which statement explains why the rate of reaction increases?

The decomposition of hydrogen peroxide, $\text{H}_2\text{O}_2$, is catalyzed by manganese(IV) oxide, $\text{MnO}_2$. Which row describes the effect of the catalyst on the activation energy and the overall enthalpy change, $\Delta H$, of this reaction?

A synthetic polymer has the repeating structure shown: $\text{---NH---(CH}_2\text{)}_6\text{---NH---CO---(CH}_2\text{)}_4\text{---CO---}$. Which type of polymerisation produces this polymer, and what is the small molecule released during the process?

An addition polymer has the repeating unit structure: $\text{---(CH}_2\text{---CH(CH}_3\text{))}_n\text{---}$. Which monomer is used to produce this polymer?

Concentrated aqueous sodium chloride is electrolysed using inert platinum electrodes. Which products are discharged at the cathode and the anode?

Aqueous copper(II) sulfate is electrolysed using active copper electrodes. Which row correctly describes the change in mass of each electrode?

A student wants to prepare a pure, dry sample of the insoluble salt, barium sulfate, $\text{BaSO}_4$. Which pair of solutions should be mixed together to achieve this?

The reaction between hydrogen and chlorine gas to form hydrogen chloride gas is exothermic: $\text{H}_2\text{(g)} + \text{Cl}_2\text{(g)} \rightarrow 2\text{HCl(g)}$. Which statement explains why this reaction is exothermic?

A student investigates the reaction between marble chips (calcium carbonate) and excess dilute nitric acid. Which change in conditions increases the initial rate of reaction without increasing the total volume of carbon dioxide gas collected at the end of the reaction?

Which row correctly describes the effect of adding a catalyst to a reaction mixture of iron(II) ions and acidified hydrogen peroxide at a constant temperature?

A synthetic polymer is made by reacting a dicarboxylic acid with a diol. Which row correctly identifies the type of polymerisation and the functional group linking the monomer units?

A section of a synthetic addition polymer chain is shown: -CH2-CH(C6H5)-CH2-CH(C6H5)-. Which compound is the monomer used to prepare this polymer?

Aqueous copper(II) chloride is electrolysed using inert platinum electrodes. Which ionic half-equations represent the reactions occurring at each electrode?

Which statement is correct for the electrolysis of molten lead(II) bromide using inert carbon electrodes?

A student wants to prepare a pure, dry sample of barium sulfate. Which pair of aqueous solutions should be mixed together to prepare barium sulfate by precipitation?

What is the volume of hydrogen gas, measured at room temperature and pressure (r.t.p.), produced when 5.4 g of aluminium reacts completely with excess dilute hydrochloric acid? [Ar(Al) = 27; the volume of one mole of gas at r.t.p. is 24 dm3]

In a series of experiments, dilute hydrochloric acid reacts with excess zinc. The temperature of the reaction mixture is increased from 20 °C to 30 °C, and the concentration of the acid is increased from 0.5 mol/dm³ to 1.0 mol/dm³. Which row describes the effect of these combined changes on the collision frequency and the percentage of collisions with energy greater than or equal to the activation energy, \(E_a\)?

Manganese(IV) oxide is used as a catalyst in the decomposition of hydrogen peroxide. How does the addition of this catalyst affect the activation energy and the enthalpy change, \(\Delta H\), of this reaction?

A synthetic polymer is manufactured by reacting a dicarboxylic acid with a diol. Which type of polymerisation occurs and what is the type of linkage formed in the macromolecule?

Proteins are naturally occurring macromolecules. When a sample of protein is completely hydrolysed, which class of compound is formed?

Concentrated aqueous sodium chloride (brine) is electrolysed using inert carbon electrodes. Which row correctly identifies the substances produced at the anode and at the cathode?

Molten lead(II) bromide is electrolysed using graphite electrodes. What is the ionic half-equation for the chemical reaction occurring at the negative electrode (cathode)?

A student wants to prepare a pure, dry sample of the insoluble salt barium sulfate, \(BaSO_4\). Which pair of aqueous solutions is most suitable to mix together?

Hydrated copper(II) sulfate crystals can be prepared by reacting excess copper(II) oxide with dilute sulfuric acid. Which sequence of experimental steps describes the correct method?

A reaction of excess dilute hydrochloric acid with a fixed mass of zinc powder is carried out at \(20^\circ\text{C}\). The volume of hydrogen gas produced is plotted over time to give Curve 1. The experiment is repeated under the same conditions but using the same mass of larger zinc pieces instead of zinc powder, to give Curve 2.

Which statement correctly describes Curve 2 compared to Curve 1?

Why does an increase in temperature increase the rate of a chemical reaction?

1. The particles have more kinetic energy, which increases the frequency of collisions.
2. The activation energy of the reaction is lowered.
3. A greater proportion of the colliding particles have energy equal to or greater than the activation energy.

A condensation polymer is formed when monomers react with the loss of small molecules. Which pair of monomers reacts to form a polyester?

A section of an addition polymer chain is shown below.

\(-CH_2-CH(Cl)-CH_2-CH(Cl)-CH_2-CH(Cl)-\)

What is the name of the monomer used to produce this polymer?

Concentrated aqueous sodium chloride is electrolysed using inert carbon electrodes. Which row correctly describes the products at the electrodes and the change in pH of the electrolyte near the cathode?

Which setup is correct for electroplating a steel spoon with a layer of silver?

Which experimental method is most suitable for preparing a pure, dry sample of the insoluble salt, barium sulfate?

Copper(II) sulfate crystals are prepared by adding excess copper(II) oxide to hot dilute sulfuric acid. Why is an excess of copper(II) oxide used?

The decomposition of aqueous hydrogen peroxide is catalysed by manganese(IV) oxide. Which statement describes how the catalyst increases the rate of this reaction?

An excess of calcium carbonate chunks is reacted with dilute hydrochloric acid. The volume of carbon dioxide gas produced is measured over time. The experiment is repeated under identical conditions, but using the same mass of calcium carbonate powder instead of chunks. How do the initial rate of reaction and the total volume of carbon dioxide gas produced compare to the first experiment?

A section of an addition polymer is shown.

\(-\text{CH}_2-\text{CH}(\text{CH}_3)-\text{CH}_2-\text{CH}(\text{CH}_3)-\text{CH}_2-\text{CH}(\text{CH}_3)-\)

What is the correct name and formula of the monomer used to produce this polymer?

Which row correctly describes the monomers and type of linkage found in a typical polyester such as Terylene (PET)?

Concentrated aqueous sodium chloride is electrolysed using inert carbon electrodes. Which products are formed at the anode and cathode?

Molten lead(II) bromide is electrolysed using inert platinum electrodes. Which ionic half-equation correctly represents the reaction occurring at the negative electrode (cathode)?

A student wants to prepare a pure, dry sample of the insoluble salt, barium sulfate. Which pair of aqueous solutions should be mixed together, and what is the final step to obtain the dry solid?

The equation represents a redox reaction.

\(\text{Fe}_2\text{O}_3 + 3\text{CO} \rightarrow 2\text{Fe} + 3\text{CO}_2\)

Which statement about this reaction is correct?

The reaction between calcium carbonate and dilute hydrochloric acid is investigated: \(\text{CaCO}_3\text{(s)} + 2\text{HCl(aq)} \to \text{CaCl}_2\text{(aq)} + \text{H}_2\text{O(l)} + \text{CO}_2\text{(g)}\). (a) Draw a labelled diagram of the apparatus that can be used to measure the volume of carbon dioxide gas produced over time. [3] (b) Describe how the rate of reaction changes from the start of the reaction until it stops. Explain this change in terms of particle collision theory. [4] (c) State and explain the effect of increasing the concentration of hydrochloric acid on the rate of reaction. Use collision theory in your explanation. [3] (d) Describe the expected difference in the reaction progress curve if the reaction is repeated at a higher temperature. Explain your answer. [3]

This question is about polymers. (a) Poly(lactic acid), PLA, is a biodegradable condensation polymer. (i) State what is meant by the term biodegradable. [1] (ii) The monomer for PLA is 2-hydroxypropanoic acid (lactic acid), \(\text{CH}_3\text{CH(OH)COOH}\). Draw the structure of poly(lactic acid) showing two repeat units. Show all the atoms and bonds in the ester linkages. [3] (b) Nylon-6,6 is a synthetic polyamide. (i) State the names of the two functional groups that react to form a polyamide. [2] (ii) Draw the structures of the two monomers that react to form the polyamide represented by the structure: \(\text{[-HN-(CH}_2\text{)}_6\text{-NH-CO-(CH}_2\text{)}_4\text{-CO-]}\). [3] (c) Compare addition polymerisation and condensation polymerisation in terms of the types of monomer used and the products formed. [4]

The electrolysis of concentrated aqueous copper(II) chloride is carried out using carbon (graphite) electrodes. (a) State the observations and name the product formed at: (i) the anode (positive electrode) [2] (ii) the cathode (negative electrode). [2] (b) Write the ionic half-equations for the reactions occurring at: (i) the anode [1.5] (ii) the cathode. [1.5] (c) The electrolysis of dilute sulfuric acid is carried out using inert platinum electrodes. (i) Name the product formed at each electrode. [2] (ii) Write the ionic half-equation for the reaction at the anode. [2] (iii) Describe how the concentration of the acid changes during this electrolysis and explain your answer. [3]

This question is about the preparation of salts. (a) Barium sulfate is an insoluble salt that can be prepared by a precipitation reaction. (i) Name two soluble salts that could be mixed to prepare barium sulfate. [2] (ii) Describe the steps required to obtain a pure, dry sample of barium sulfate from the reaction mixture. [4] (iii) Write the ionic equation, with state symbols, for this precipitation reaction. [2] (b) Zinc sulfate is a soluble salt. It can be prepared by reacting excess zinc oxide with dilute sulfuric acid. (i) Explain why excess zinc oxide is used rather than excess sulfuric acid. [2] (ii) State how the excess zinc oxide is removed from the reaction mixture. [1] (iii) Describe how hydrated zinc sulfate crystals are obtained from the zinc sulfate solution. [2]

A student carries out an experiment to determine the formula of hydrated copper(II) sulfate crystals, \(\text{CuSO}_4 \cdot x\text{H}_2\text{O}\). The student heats a known mass of hydrated copper(II) sulfate in a crucible. The data obtained is: Mass of empty crucible = 15.40 g; Mass of crucible + hydrated copper(II) sulfate = 20.39 g; Mass of crucible + anhydrous copper(II) sulfate (after heating to constant mass) = 18.59 g. (a) State how the student can ensure that all the water of crystallisation has been completely removed. [1] (b) Calculate: (i) the mass of anhydrous copper(II) sulfate obtained. [1] (ii) the mass of water of crystallisation lost. [1] (iii) the number of moles of anhydrous copper(II) sulfate (Relative formula mass: \(\text{CuSO}_4 = 160\)). [2] (iv) the number of moles of water lost (Relative formula mass: \(\text{H}_2\text{O} = 18\)). [2] (v) the value of \(x\) in \(\text{CuSO}_4 \cdot x\text{H}_2\text{O}\). [2] (c) State the colour change observed when water is added to anhydrous copper(II) sulfate. [2] (d) Write the chemical equation for the reversible reaction that occurs when hydrated copper(II) sulfate is heated. [2]

Methanol is manufactured industrially by the reversible reaction between carbon monoxide and hydrogen: \(\text{CO(g)} + 2\text{H}_2\text{(g)} \rightleftharpoons \text{CH}_3\text{OH(g)}\), \(\Delta H = -91\text{ kJ/mol}\). (a) State and explain the effect of increasing the temperature on: (i) the rate of the forward reaction [2] (ii) the yield of methanol at equilibrium. [3] (b) State and explain the effect of increasing the pressure on: (i) the rate of the forward reaction [2] (ii) the yield of methanol at equilibrium. [3] (c) A catalyst is used in this process. (i) Explain why a catalyst increases the rate of reaction. [2] (ii) State the effect of the catalyst on the yield of methanol at equilibrium. [2]

A student investigates the rate of the catalytic decomposition of aqueous hydrogen peroxide, \(\text{H}_2\text{O}_2\), using manganese(IV) oxide, \(\text{MnO}_2\), as a catalyst. The equation for the reaction is:

\[2\text{H}_2\text{O}_2(\text{aq}) \rightarrow 2\text{H}_2\text{O}(\text{l}) + \text{O}_2(\text{g})\]

(i) Name the piece of apparatus used to collect and measure the volume of oxygen gas produced. [1]

(ii) State how the student could ensure that the volume of liquid hydrogen peroxide is measured as accurately as possible. [1]

(iii) The table shows the volume of oxygen gas collected at regular intervals in Experiment 1 at \(25\text{ }^\circ\text{C}\).

| Time / s | 0 | 20 | 40 | 60 | 80 | 100 | 120 |
| :--- | :--- | :--- | :--- | :--- | :--- | :--- | :--- |
| Volume of \(\text{O}_2\) / \(\text{cm}^3\) | 0 | 15 | 26 | 34 | 38 | 40 | 40 |

Explain why the rate of reaction is fastest at the start of the experiment. [2]

(iv) Describe how the shape of a graph of volume of gas against time would change if the experiment were repeated at \(40\text{ }^\circ\text{C}\) with all other variables kept constant. [3]

(v) Outline an experimental procedure to prove that the manganese(IV) oxide acts as a catalyst and is not chemically consumed during the reaction. [3]

A student investigates the electrolysis of concentrated aqueous sodium chloride (brine) using inert carbon (graphite) electrodes in a U-tube.

(i) State the observations made at each electrode during the electrolysis:
Anode (positive electrode): [1]
Cathode (negative electrode): [1]

(ii) A few drops of universal indicator are added to the solution around the cathode during the electrolysis. State the colour change observed and explain why this change occurs. [3]

(iii) Name the gas produced at the anode and describe a chemical test to confirm its identity. [2]

(iv) A student wants to modify the apparatus to electroplate a steel key with a thin layer of copper. State the required components for this modified setup:
Material for the anode: [1]
Material for the cathode: [1]
Electrolyte solution: [1]

A student prepares a pure, dry sample of hydrated copper(II) sulfate crystals, \(\text{CuSO}_4 \cdot 5\text{H}_2\text{O}\), from insoluble copper(II) oxide powder and dilute sulfuric acid.

(i) State why copper(II) oxide is added in excess to the dilute sulfuric acid. [1]

(ii) State the method used to separate the excess copper(II) oxide from the mixture. [1]

(iii) Describe how the student can obtain large, well-formed crystals of hydrated copper(II) sulfate from the filtrate. Do not describe how to dry the crystals in your answer. [3]

(iv) State how the crystals can be dried safely without losing their water of crystallisation. [1]

(v) Copper(II) carbonate can also be used instead of copper(II) oxide.
- State one different observation that would be made during the reaction. [1]
- Write the balanced chemical equation for the reaction between copper(II) carbonate and dilute sulfuric acid. [2]
- State the chemical test used to identify the gas produced. [1]

A student is provided with three unlabelled bottles containing different liquid monomers used in polymerisation:

- Monomer A: \(\text{CH}_2=\text{CHCOOH}\) (propenoic acid)
- Monomer B: \(\text{HOOC}(\text{CH}_2)_4\text{COOH}\) (hexanedioic acid)
- Monomer C: \(\text{H}_2\text{N}(\text{CH}_2)_6\text{NH}_2\) (hexane-1,6-diamine)

(i) Describe a chemical test to distinguish Monomer A from Monomer B, including the observations for both monomers. [3]

(ii) Monomer B and Monomer C react together to form a synthetic polymer.
- Name the type of polymerisation reaction that occurs. [1]
- Name the small molecule released as a byproduct during this reaction. [1]
- Draw the structure of the linkage formed between Monomer B and Monomer C, showing all atoms and bonds in the linkage. [3]

(iii) Monomer A can undergo addition polymerisation to form poly(propenoic acid). Draw the structure of poly(propenoic acid) showing two repeat units. [2]