2023 Cambridge IGCSE Chemistry (0620) Practice Paper with Answers

What is the maximum volume of carbon dioxide, measured at room temperature and pressure (rtp), produced when \(10.0\text{ g}\) of calcium carbonate (\(M_r = 100\)) reacts completely with excess dilute hydrochloric acid? (1 mol of gas occupies \(24.0\text{ dm}^3\) at rtp)

Which statement explains why increasing the temperature increases the rate of a chemical reaction?

During the electrolysis of concentrated aqueous sodium chloride using inert electrodes, which products are formed at the electrodes?

Which statement about the halogens and their halide ions is correct?

Which linkage is present in nylon?

Two separate experiments are carried out. In Experiment 1, \(10\text{ cm}^3\) of \(1.0\text{ mol/dm}^3\) hydrochloric acid is reacted with excess zinc. In Experiment 2, \(10\text{ cm}^3\) of \(1.0\text{ mol/dm}^3\) ethanoic acid is reacted with excess zinc. Which statement is correct?

The equation for the Haber process is: \(\text{N}_2(\text{g}) + 3\text{H}_2(\text{g}) \rightleftharpoons 2\text{NH}_3(\text{g})\) with a forward enthalpy change of \(-92\text{ kJ/mol}\). Which set of changes will both shift the position of equilibrium to the right?

A solid compound, X, is dissolved in water. When aqueous sodium hydroxide is added to the solution of X, a green precipitate is formed which is insoluble in excess. When dilute nitric acid and aqueous barium nitrate are added to another portion of the solution, a white precipitate is formed. What is compound X?

A 1.50 g sample of an organic compound, X, contains only carbon, hydrogen and oxygen. Complete combustion of X in excess oxygen produces 2.20 g of carbon dioxide, \(CO_2\), and 0.90 g of water, \(H_2O\). What is the empirical formula of X?

Excess calcium carbonate (marble chips) reacts with 50 \(cm^3\) of 1.0 \(mol/dm^3\) hydrochloric acid to produce carbon dioxide gas. The volume of gas released is plotted against time to give Curve X. The experiment is repeated under different conditions, keeping the mass of calcium carbonate the same and in excess. Which set of conditions produces Curve Y, where the reaction rate is slower but the final volume of gas collected is the same?

An aqueous solution of copper(II) sulfate is electrolysed using inert carbon electrodes. Which row correctly describes the observations at each electrode and the change in pH of the solution?

In which reaction does the underlined substance act as a proton acceptor?

The structure of a synthetic polymer is represented as: \(-NH-\square-NH-CO-\Delta-CO-NH-\square-NH-CO-\Delta-CO-\). Which monomers are used to make this polymer?

The results of three displacement experiments involving three halogens, \(X_2\), \(Y_2\), and \(Z_2\), and their halide ions, \(X^-\), \(Y^-\), and \(Z^-\), are described. Experiment 1: \(X_2\) reacts with \(Y^-\) to turn a colourless solution orange-brown. Experiment 2: \(Y_2\) reacts with \(Z^-\) to turn a colourless solution dark brown. Experiment 3: \(Z_2\) is added to \(X^-\), and no reaction occurs. What are the correct identities of halogens X, Y and Z?

An unknown salt, W, is dissolved in water to make a solution. Portions of this solution are tested. Test 1: Addition of aqueous sodium hydroxide produces a green precipitate that is insoluble in excess sodium hydroxide. Test 2: Addition of dilute nitric acid followed by aqueous barium nitrate produces a white precipitate. What is the identity of W?

The equation for the reversible reaction to produce methanol is shown: \(CO(g) + 2H_2(g) \rightleftharpoons CH_3OH(g)\) (where the forward reaction is exothermic). The temperature of the equilibrium mixture is increased while keeping the pressure constant. How do the yield of methanol and the rate of the forward reaction change?

An electrolysis experiment is set up using inert carbon electrodes in concentrated aqueous sodium chloride. Which row correctly identifies the products formed at each electrode and the change in pH of the electrolyte during the electrolysis?

The contact process involves the reversible reaction: \(2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g)\), where the forward reaction is exothermic. Which set of reaction conditions would produce the highest equilibrium yield of sulfur trioxide?

A student investigates the reaction between excess calcium carbonate and dilute hydrochloric acid. Which change in conditions increases the initial rate of reaction but does not change the total volume of carbon dioxide gas collected at the end of the reaction?

Calcium carbide, \(CaC_2\), reacts with water to form ethyne gas, \(C_2H_2\), and calcium hydroxide, \(Ca(OH)_2\). The equation for the reaction is: \(CaC_2(s) + 2H_2O(l) \rightarrow Ca(OH)_2(aq) + C_2H_2(g)\). What volume of ethyne gas, measured at room temperature and pressure (rtp), is produced when \(16.0 \text{ g}\) of calcium carbide (\(M_r = 64.0\)) reacts completely with excess water? (The molar volume of any gas at rtp is \(24.0 \text{ dm}^3\).)

In the reaction shown, which substance is oxidized and what is the change in the oxidation state of sulfur? \(2FeCl_3(aq) + H_2S(g) \rightarrow 2FeCl_2(aq) + S(s) + 2HCl(aq)\)

Terylene is a synthetic polyester. Which statement about the formation of Terylene is correct?

Which statement correctly compares a \(0.1 \text{ mol/dm}^3\) solution of hydrochloric acid with a \(0.1 \text{ mol/dm}^3\) solution of ethanoic acid?

An aqueous solution of salt X is tested. Addition of aqueous sodium hydroxide produces a green precipitate that is insoluble in excess. Addition of dilute nitric acid followed by aqueous barium nitrate produces a white precipitate. What is the identity of salt X?

An element X has two main isotopes, \(^{63}\text{X}\) and \(^{65}\text{X}\). The relative atomic mass of X is 63.6. Which statement about these isotopes is correct?

A sample of 2.10 g of a group II metal carbonate, \(\text{XCO}_3\), is fully decomposed by heating to form a metal oxide and carbon dioxide gas. The volume of carbon dioxide gas collected at rtp is 600 cm\(^3\). What is the identity of metal X?

A student investigates the rate of reaction between marble chips (calcium carbonate) and dilute hydrochloric acid: \(\text{CaCO}_3(\text{s}) + 2\text{HCl}(\text{aq}) \rightarrow \text{CaCl}_2(\text{aq}) + \text{H}_2\text{O}(\text{l}) + \text{CO}_2(\text{g})\). In Experiment 1, 5.0 g of large marble chips are reacted with 50 cm\(^3\) of 1.0 mol/dm\(^3\) \(\text{HCl}\) at 20 \(^{\circ}\)C. Which change in conditions for Experiment 2 would result in a faster initial rate of reaction but produce the same final volume of carbon dioxide gas?

Equal volumes of two different acids are prepared: Acid P is 0.1 mol/dm\(^3\) hydrochloric acid, and Acid Q is 0.1 mol/dm\(^3\) ethanoic acid. Which statement about these two solutions is correct?

Halogens and their halide solutions undergo displacement reactions based on their reactivity. Which mixture results in a displacement reaction and what is the final appearance of the mixture?

A polymer has the following repeating unit: \(- \text{O} - \text{CH}_2 - \text{CH}_2 - \text{O} - \text{CO} - \text{CH}_2 - \text{CH}_2 - \text{CO} -\). Which statement about this polymer is correct?

An aqueous solution of sodium sulfate, \(\text{Na}_2\text{SO}_4\), is electrolysed using inert carbon electrodes. A few drops of universal indicator are added to the solution, which is initially green (neutral pH 7). What is observed at each electrode after the current has passed for several minutes?

Iron(III) chloride reacts with hydrogen sulfide gas according to the equation: \(2\text{FeCl}_3(\text{aq}) + \text{H}_2\text{S}(\text{g}) \rightarrow 2\text{FeCl}_2(\text{aq}) + \text{S}(\text{s}) + 2\text{HCl}(\text{aq})\). Which statement describes the redox processes in this reaction?

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

A student investigates the rate of reaction between marble chips (excess) and dilute hydrochloric acid. The volume of carbon dioxide gas collected is measured over time.

The experiment is repeated using the same mass of marble chips and the same volume of hydrochloric acid, but with one change: the concentration of the hydrochloric acid is doubled, while its volume is halved.

How does the second experiment compare to the first?

The following reversible reaction reaches dynamic equilibrium in a sealed container:

\[2SO_2(g) + O_2(g) \rightleftharpoons 2SO_3(g) \quad \Delta H = -197\text{ kJ/mol}\]

Which set of conditions will produce the greatest yield of sulfur trioxide, \(SO_3(g)\), at equilibrium?

What is the minimum mass of pure carbon, \(C\), required to completely reduce 80.0 g of iron(III) oxide, \(Fe_2O_3\), according to the equation below?

\[2Fe_2O_3(s) + 3C(s) \rightarrow 4Fe(s) + 3CO_2(g)\]

[Relative atomic masses, \(A_r\): \(C = 12\), \(O = 16\), \(Fe = 56\)]

A section of a synthetic polymer is shown:

\[-CH_2-CH(Cl)-CH_2-CH(Cl)-CH_2-CH(Cl)-\]

Which statement about this polymer is correct?

Which statement correctly describes a property of a weak acid, such as ethanoic acid, compared to a strong acid of the same concentration?

Aqueous chlorine, bromine water, and iodine water are added separately to solutions of potassium halides.

Which row correctly describes the observations?

A solid mixture containing two salts is dissolved in water to make a solution.

- Addition of dilute nitric acid followed by aqueous silver nitrate produces a yellow precipitate.
- Addition of excess aqueous sodium hydroxide produces a green precipitate that is insoluble in excess.

Which two ions are present in the mixture?

A student investigates the rate of reaction between calcium carbonate (marble chips) and dilute hydrochloric acid:
\( \text{CaCO}_3(\text{s}) + 2\text{HCl}(\text{aq}) \rightarrow \text{CaCl}_2(\text{aq}) + \text{H}_2\text{O}(\text{l}) + \text{CO}_2(\text{g}) \)

(a) Describe how the volume of gas evolved could be measured over time, naming the apparatus used. [3 marks]
(b) Explain, in terms of collision theory, how increasing the concentration of hydrochloric acid increases the rate of this reaction. [3 marks]
(c) The student repeats the experiment using the same mass of calcium carbonate but as a fine powder instead of large chips.
(i) Describe and explain the effect of this change on the rate of reaction. [3 marks]
(ii) State and explain what happens to the total volume of carbon dioxide gas produced. [2 marks]
(d) Describe the role of a catalyst in terms of activation energy and collision theory. [2.33 marks]

Halogens are Group VII elements. They show trends in physical and chemical properties.

(a) State the trend down Group VII for:
(i) the color intensity of the halogens. [1 mark]
(ii) the boiling point of the halogens. [1 mark]
(iii) the reactivity of the halogens. [1 mark]
(b) Chlorine gas is bubbled into a solution of aqueous potassium bromide.
(i) State the observation for this reaction. [1 mark]
(ii) Write an ionic equation, including state symbols, for this reaction. [3 marks]
(iii) Explain, in terms of electron transfer, which species is oxidised. [2 marks]
(c) Draw a dot-and-cross diagram to show the arrangement of outer-shell electrons in a molecule of hydrogen fluoride, HF. [2 marks]
(d) Explain why aqueous hydrogen fluoride behaves as a weak acid. [1.33 marks]

A solid mixture, \( \mathbf{Y} \), contains one cation and two different anions. A student performs a series of qualitative tests on \( \mathbf{Y} \).

(a) Aqueous sodium hydroxide is added to an aqueous solution of \( \mathbf{Y} \). A green precipitate is formed, which does not dissolve in excess sodium hydroxide.
(i) Identify the cation present. [1 mark]
(ii) Write the ionic equation, including state symbols, for the formation of this green precipitate. [2 marks]
(b) Dilute nitric acid is added to solid \( \mathbf{Y} \). Effervescence is observed, producing a colorless gas that forms a white precipitate when bubbled through limewater.
(i) Identify one of the anions in \( \mathbf{Y} \). [1 mark]
(ii) Name the gas produced. [1 mark]
(c) To another sample of the solution of \( \mathbf{Y} \), dilute nitric acid is added, followed by aqueous barium nitrate. A white precipitate is formed.
(i) Identify the second anion in \( \mathbf{Y} \). [1 mark]
(ii) Write the ionic equation for the formation of this white precipitate. [2 marks]
(d) Describe a chemical test, including reagents and observations, to distinguish between:
(i) Carbon dioxide and sulfur dioxide gas. [3.33 marks]
(ii) Aqueous iron(III) ions and aqueous aluminium ions. [2 marks]

Methanol is produced industrially by the reversible reaction of carbon monoxide and hydrogen:
\( \text{CO}(\text{g}) + 2\text{H}_2(\text{g}) \rightleftharpoons \text{CH}_3\text{OH}(\text{g}) \) \(\Delta H = -91\text{ kJ/mol} \)

(a) State two characteristics of a reaction at dynamic equilibrium. [2 marks]
(b) Explain the effect of the following changes on the position of equilibrium:
(i) Increasing the pressure. [3 marks]
(ii) Increasing the temperature. [3 marks]
(c) The industrial process is carried out at about \( 250\ ^\circ\text{C} \) and \( 50-100\text{ atm} \). Explain why a temperature of \( 250\ ^\circ\text{C} \) is used rather than a much lower temperature, even though a lower temperature would give a higher equilibrium yield. [2 marks]
(d) Define the term catalyst and name the catalyst used in this reaction. [3.33 marks]

A 5.30 g sample of impure anhydrous sodium carbonate, \( \text{Na}_2\text{CO}_3 \), was dissolved in water to make a 250 \( \text{cm}^3 \) solution. A 25.0 \( \text{cm}^3 \) portion of this solution was titrated against 0.200 \( \text{mol/dm}^3 \) hydrochloric acid. It required 22.5 \( \text{cm}^3 \) of the acid for complete neutralisation:
\( \text{Na}_2\text{CO}_3(\text{aq}) + 2\text{HCl}(\text{aq}) \rightarrow 2\text{NaCl}(\text{aq}) + \text{H}_2\text{O}(\text{l}) + \text{CO}_2(\text{g}) \)

(a) Calculate the number of moles of hydrochloric acid used in the titration. [2 marks]
(b) Determine the number of moles of sodium carbonate in the 25.0 \( \text{cm}^3 \) portion. [2 marks]
(c) Calculate the number of moles of sodium carbonate in the 250 \( \text{cm}^3 \) solution. [2 marks]
(d) Calculate the mass of sodium carbonate in the 250 \( \text{cm}^3 \) solution. [Relative formula mass: \( \text{Na}_2\text{CO}_3 = 106 \)] [2 marks]
(e) Calculate the percentage purity of the original sample of sodium carbonate. [2.33 marks]
(f) A separate 4.29 g sample of hydrated sodium carbonate, \( \text{Na}_2\text{CO}_3 \cdot x\text{H}_2\text{O} \), was heated strongly to constant mass. The mass of the anhydrous residue was 1.59 g. Calculate the value of \( x \). [3 marks]

Synthetic and natural polymers have many important applications.

(a) Nylon-6,6 is a synthetic polyamide made by condensation polymerisation.
(i) State the meaning of the term condensation polymerisation. [2 marks]
(ii) Nylon-6,6 is made from 1,6-diaminohexane and hexanedioic acid. Draw the block structures of these two monomers, showing all the atoms and bonds in their functional groups. [2 marks]
(iii) Draw a section of the polymer chain of nylon-6,6 showing one amide linkage. Show all bonds in the linkage. [2 marks]
(b) Terylene is a polyester.
(i) State the name of the two functional groups that react together to form Terylene. [2 marks]
(ii) State one major use of Terylene. [1 mark]
(c) Proteins are natural polymers.
(i) Name the type of monomer that forms proteins. [1 mark]
(ii) State the name of the linkage in proteins and draw its structure. [2.33 marks]
(iii) Name the process by which proteins are broken down into their monomers in the laboratory. [1 mark]

A student wants to plan an investigation to determine the solubility of potassium nitrate, \(\text{KNO}_3\), in water at different temperatures. Solubility is defined as the maximum mass of solute that can dissolve in \(100\text{ g}\) of water at a specified temperature. The student is provided with: solid potassium nitrate, distilled water, and standard laboratory apparatus (beakers, test-tubes, balance, thermometer, Bunsen burner, tripod, gauze, measuring cylinders, glass rod). (a) Name a suitable piece of apparatus to measure exactly \(20.0\text{ cm}^3\) of distilled water. [1] (b) Describe how the student could prepare a saturated solution of potassium nitrate at a specific temperature (e.g. \(40\text{ }^\circ\text{C}\)) and ensure that no solid remains suspended in the liquid before further steps. [3] (c) Once a clear, saturated solution at \(40\text{ }^\circ\text{C}\) is obtained, describe the experimental steps required to determine the mass of dissolved potassium nitrate in a known volume of this solution. [4] (d) Suggest two safety precautions that should be taken during this investigation. [2]

A student investigates the rate of reaction between marble chips (calcium carbonate) and dilute hydrochloric acid: \(\text{CaCO}_3\text{(s)} + 2\text{HCl(aq)} \rightarrow \text{CaCl}_2\text{(aq)} + \text{H}_2\text{O(l)} + \text{CO}_2\text{(g)}\). They measure the volume of carbon dioxide gas collected over time using a gas syringe. (a) Draw a labelled diagram of the assembled apparatus that could be used to carry out this experiment and collect the gas. [3] (b) The gas syringe readings at different times during the experiment are recorded: At \(0\text{ s}\): \(0\text{ cm}^3\); At \(30\text{ s}\): \(24\text{ cm}^3\); At \(60\text{ s}\): \(40\text{ cm}^3\); At \(90\text{ s}\): \(51\text{ cm}^3\); At \(120\text{ s}\): \(58\text{ cm}^3\); At \(150\text{ s}\): \(60\text{ cm}^3\); At \(180\text{ s}\): \(60\text{ cm}^3\). (i) State the time at which the reaction stopped. [1] (ii) Explain your answer to (b)(i). [1] (c) Calculate the average rate of reaction between \(0\text{ s}\) and \(60\text{ s}\). Show your working and state the units. [2] (d) The student repeats the experiment using the same mass of calcium carbonate but as a fine powder instead of large chips. (i) Describe how the rate of reaction changes. [1] (ii) Explain this change in terms of particle collision theory. [2]

Two substances, Solid E and Liquid F, were analysed. Solid E was a green transition metal salt. Liquid F was an aqueous solution of an acid. (a) Solid E was dissolved in distilled water to make Solution E. To a \(2\text{ cm}^3\) portion of Solution E, aqueous sodium hydroxide was added dropwise until in excess. Observation: A green precipitate was formed, which was insoluble in excess. Identify the cation present in Solid E. [1] (b) To another \(2\text{ cm}^3\) portion of Solution E, dilute nitric acid and then aqueous barium nitrate were added. Observation: A white precipitate was formed. Identify the anion present in Solid E. [1] (c) Deduce the chemical formula of Solid E. [1] (d) A sample of Solid E was heated strongly in a dry test-tube. A gas was evolved which turned a piece of damp blue litmus paper red, and then bleached it. (i) Identify this gas. [1] (ii) Describe a chemical test for this gas, other than using indicator paper, and state the expected observation. [2] (e) Liquid F was tested. (i) When a piece of magnesium ribbon was added to Liquid F, a gas was evolved. Describe a test to identify this gas and state the expected positive observation. [2] (ii) When aqueous silver nitrate was added to Liquid F, a white precipitate was formed. Identify Liquid F. [2]

A student determined the concentration of a solution of sodium hydroxide, \(\text{NaOH}\), by titrating it against a standard solution of sulfuric acid, \(\text{H}_2\text{SO}_4\), of concentration \(0.0500\text{ mol/dm}^3\). The student filled a burette with the sulfuric acid. They used a volumetric pipette to transfer \(25.0\text{ cm}^3\) of the sodium hydroxide solution into a conical flask, and added a few drops of methyl orange indicator. (a) Describe the colour change of the methyl orange indicator at the end-point of this titration (acid added to alkali). [2] From: ......................... To: ......................... (b) The student carried out three titrations: Titration 1: Initial reading was \(0.40\text{ cm}^3\), final reading was \(24.60\text{ cm}^3\); Titration 2: Initial reading was \(1.20\text{ cm}^3\), final reading was \(25.50\text{ cm}^3\); Titration 3: Initial reading was \(2.10\text{ cm}^3\), final reading was \(26.20\text{ cm}^3\). (i) Complete the table by filling in the values for the volume of acid added (titre) in each titration. [3] | Titration number | Final reading / \(\text{cm}^3\) | Initial reading / \(\text{cm}^3\) | Volume of acid added / \(\text{cm}^3\) | |---|---|---|---| | 1 | 24.60 | 0.40 | | | 2 | 25.50 | 1.20 | | | 3 | 26.20 | 2.10 | | (ii) Calculate the mean titre of sulfuric acid to be used in the calculation. Show your working. [2] (c) Calculate the concentration of the sodium hydroxide solution in \(\text{mol/dm}^3\). The equation for the reaction is: \(2\text{NaOH(aq)} + \text{H}_2\text{SO}_4\text{(aq)} \rightarrow \text{Na}_2\text{SO}_4\text{(aq)} + 2\text{H}_2\text{O(l)}\) [3]