2024 Cambridge IGCSE Chemistry (0620) 模擬試題連答案詳解

A substance has a melting point of \(-183^\circ\text{C}\) and a boiling point of \(-161^\circ\text{C}\). What is its physical state at \(-170^\circ\text{C}\) and at \(25^\circ\text{C}\)?

An atom of phosphorus is represented as \(^{31}_{15}\text{P}\). How many nucleons and how many neutrons does this atom contain?

A student wants to obtain pure liquid water from an aqueous solution of copper(II) sulfate. Which separation method should be used?

Which chemical process is endothermic?

Dilute hydrochloric acid is added to solid sodium carbonate. Which products are formed in this reaction?

Which row correctly describes the trends in colour and physical state of the Group VII elements as the group is descended from chlorine to iodine?

Which atmospheric pollutant is primarily responsible for the formation of acid rain?

Which statement correctly describes a homologous series?

The table shows the melting and boiling points of four substances.

Which substance is a liquid at \(50^\circ\text{C}\)?

| substance | melting point / \(^\circ\text{C}\) | boiling point / \(^\circ\text{C}\) |
| :---: | :---: | :---: |
| A | -110 | -15 |
| B | -10 | 80 |
| C | 60 | 250 |
| D | 120 | 330 |

An atom contains 17 protons, 18 neutrons and 17 electrons.

What is the nucleon number of this atom?

Magnesium reacts with oxygen to form magnesium oxide, which is an ionic compound.

What happens to the magnesium atoms during this reaction?

Molten lead(II) bromide is electrolysed using carbon electrodes.

Which row identifies the products formed at each electrode?

| | product at the negative electrode (cathode) | product at the positive electrode (anode) |
| :---: | :---: | :---: |
| A | bromine | lead |
| B | lead | bromine |
| C | hydrogen | oxygen |
| D | lead | oxygen |

Which process is an exothermic reaction?

An aqueous solution of substance Y has a pH of 3.

What are the colours of methyl orange and thymolphthalein indicators when added separately to this solution?

| | colour of methyl orange | colour of thymolphthalein |
| :---: | :---: | :---: |
| A | red | colourless |
| B | red | blue |
| C | yellow | colourless |
| D | yellow | blue |

Potassium is a Group I element in the Periodic Table.

Which statements about potassium are correct?

1 It is a soft metal with a low density.
2 It reacts violently with cold water.
3 It forms an alkaline solution when it reacts with water.
4 It is stored under oil to prevent reaction with air.

Fermentation is used to manufacture ethanol from glucose.

Which row shows the correct conditions required for fermentation?

| | temperature | catalyst | oxygen |
| :---: | :---: | :---: | :---: |
| A | \(35^\circ\text{C}\) | yeast | absent |
| B | \(35^\circ\text{C}\) | yeast | present |
| C | \(70^\circ\text{C}\) | nickel | absent |
| D | \(70^\circ\text{C}\) | nickel | present |

The table shows the melting and boiling points of four substances, W, X, Y and Z.

Substance | Melting point / °C | Boiling point / °C
--- | --- | ---
W | -114 | 78
X | -182 | -161
Y | 0 | 100
Z | 801 | 1413

Which substance is a liquid at -10 °C?

Which statement about isotopes of the same element is correct?

An atom of element X is in Group VI of the Periodic Table. What happens when X forms an ion?

During the electrolysis of molten lead(II) bromide using inert electrodes, what is produced at each electrode?

A student adds magnesium ribbon to dilute hydrochloric acid. The temperature of the mixture increases during the reaction.

Which row describes the type of reaction and the energy transfer?

A student investigates the rate of reaction between calcium carbonate and dilute hydrochloric acid.

Which change decreases the rate of this reaction?

Three unlabelled bottles contain solutions with the following pH values:
- Solution 1: pH 2
- Solution 2: pH 7
- Solution 3: pH 11

What are the colours of these solutions when a few drops of universal indicator are added?

Which statement about ethanol is correct?

The table shows the melting and boiling points of four elements, W, X, Y and Z.

| Element | Melting point / °C | Boiling point / °C |
|---|---|---|
| W | -189 | -186 |
| X | -39 | 357 |
| Y | 30 | 2403 |
| Z | 660 | 2519 |

Which element is a liquid at 25 °C?

An atom of an isotope of potassium has a nucleon number of 39. Referring to the Periodic Table, how many protons, neutrons and electrons are in this neutral atom?

Magnesium reacts with fluorine to form the ionic compound magnesium fluoride, \(MgF_2\).

What happens to the magnesium atoms in this reaction?

Molten lead(II) bromide is electrolysed using inert carbon electrodes.

Which row correctly identifies the product formed at each electrode?

Which statement about an exothermic reaction is correct?

Identical masses of calcium carbonate are reacted separately with excess dilute hydrochloric acid under different conditions.

Which reaction has the highest initial rate of reaction?

A solution has a pH of 12. Which statement describes this solution?

Ethanol is manufactured by the fermentation of glucose.

Which set of conditions is correct for this process?

An atom of phosphorus has a nucleon number of 31 and a proton number of 15. How many neutrons and electrons does this neutral atom contain?

When liquid water turns into steam, what happens to the arrangement and movement of the particles?

Which row correctly describes an exothermic chemical reaction?

A mixture contains insoluble barium sulfate, soluble sodium chloride, and water. Which sequence of steps is used to obtain a dry sample of barium sulfate and a separate solution of sodium chloride?

Metals P, Q, and R are reacted with dilute hydrochloric acid.
- Metal P reacts with dilute hydrochloric acid to produce bubbles of hydrogen.
- Metal Q does not react with dilute hydrochloric acid.
- Metal R reacts more vigorously with dilute hydrochloric acid than metal P.
What is the order of reactivity of the metals, from most reactive to least reactive?

Which statement describes the trends in the physical state and colour of the halogens as Group VII is descended?

Which pollutant gas is formed by the incomplete combustion of carbon-containing fuels?

What is the general formula of alkanes, and what are the products when an alkane undergoes complete combustion?

Which gas has the highest rate of diffusion at room temperature and pressure?

Which statement about the giant covalent structures of diamond and graphite is correct?

Concentrated aqueous sodium chloride is electrolysed using inert electrodes. Which row correctly identifies the product at each electrode and the effect on the pH of the electrolyte?

An iron pipeline is buried underground. To protect the iron from rusting, it is connected by a wire to a block of metal M. Which row correctly identifies a suitable metal M and the reason for its choice?

An organic compound X reacts with a carboxylic acid Y to form an ester with the formula \(\text{CH}_3\text{COOCH}_2\text{CH}_2\text{CH}_3\). What are the names of compound X and carboxylic acid Y?

What is the minimum volume of oxygen gas, measured at r.t.p., required for the complete combustion of \(0.2\text{ mol}\) of propane gas, \(\text{C}_3\text{H}_8\)? (The volume of one mole of any gas is \(24\text{ dm}^3\) at r.t.p.)

The structural formula of an addition polymer is shown: \(\text{---[CH}_2\text{---CH(CH}_3\text{)]}_n\text{---}\). Which monomer is used to make this polymer?

In which reaction is the underlined element oxidized?

An ion of element Y has a charge of 2+ and the formula \(^{56}_{26}\text{Y}^{2+}\). How many neutrons and electrons does this ion contain?

Which gas has the highest rate of diffusion at room temperature and pressure?

Concentrated aqueous sodium chloride is electrolysed using platinum electrodes. Which row correctly identifies the product at each electrode and the change in the electrolyte?

A series of experiments is set up to find the order of reactivity of four metals: cobalt, copper, magnesium, and tin. Cobalt displaces copper and tin from solutions of their salts, but does not displace magnesium. Tin displaces copper from solutions of copper salts. What is the correct order of reactivity of these metals, starting with the most reactive?

Ethene reacts with bromine water in an addition reaction. What is the structural formula of the product formed?

The reaction between hydrogen and fluorine to form hydrogen fluoride is shown: \( \text{H}_2\text{(g)} + \text{F}_2\text{(g)} \rightarrow 2\text{HF(g)} \). The bond energies are: H-H = 436 kJ/mol, F-F = 158 kJ/mol, H-F = 562 kJ/mol. What is the energy change for this reaction?

What is the maximum volume of carbon dioxide gas, measured at r.t.p., produced when 10.0 g of calcium carbonate (\( \text{CaCO}_3 \)) is completely reacted with excess hydrochloric acid? [Relative atomic masses: Ca=40, C=12, O=16. One mole of any gas occupies 24.0 dm3 at r.t.p.]

An aqueous solution of salt X is tested. It produces a blue-green flame in a flame test. Addition of aqueous sodium hydroxide produces a light blue precipitate that is insoluble in excess. Addition of acidified barium nitrate produces a white precipitate. What is the identity of salt X?

Equal volumes of four different gases are allowed to diffuse under identical conditions of temperature and pressure. Which gas has the highest rate of diffusion?

The table shows the melting and boiling points of four substances, P, Q, R and S.

$$\begin{array}{|c|c|c|} \hline \text{Substance} & \text{Melting point } / ^\circ\text{C} & \text{Boiling point } / ^\circ\text{C} \\ \hline \text{P} & -95 & 110 \\ \hline \text{Q} & -210 & -196 \\ \hline \text{R} & 44 & 280 \\ \hline \text{S} & 114 & 184 \\ \hline \end{array}$$

Which statement is correct?

What is the total number of hydrogen atoms in $0.25\text{ mol}$ of ethanol, $\text{C}_2\text{H}_5\text{OH}$?

[Avogadro constant, $L = 6.02 \times 10^{23}\text{ /mol}$]

Aqueous copper(II) sulfate is electrolysed using carbon (graphite) electrodes.

Which row correctly describes the product at each electrode and the change in the electrolyte solution?

$$\begin{array}{|c|c|c|c|} \hline & \text{Product at anode (+)} & \text{Product at cathode (-)} & \text{Change in electrolyte solution} \\ \hline \text{A} & \text{oxygen} & \text{copper} & \text{remains blue} \\ \hline \text{B} & \text{oxygen} & \text{copper} & \text{turns colourless} \\ \hline \text{C} & \text{copper} & \text{hydrogen} & \text{remains blue} \\ \hline \text{D} & \text{copper} & \text{hydrogen} & \text{turns colourless} \\ \hline \end{array}$$

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

Which row correctly identifies the monomers and the small molecule released during the formation of the polyester, Terylene?

$$\begin{array}{|c|c|c|} \hline & \text{Monomers} & \text{Small molecule released} \\ \hline \text{A} & \text{dicarboxylic acid + diol} & \text{water} \\ \hline \text{B} & \text{dicarboxylic acid + diamine} & \text{water} \\ \hline \text{C} & \text{dicarboxylic acid + diol} & \text{hydrogen chloride} \\ \hline \text{D} & \text{dicarboxylic acid + diamine} & \text{ammonia} \\ \hline \end{array}$$

A student performs chromatography on a mixture of food colorings. The solvent front travels $8.0\text{ cm}$ from the baseline, and a yellow spot travels $5.2\text{ cm}$ from the baseline.

What is the $R_f$ value of the yellow spot?

The table shows some properties of the Group VII elements (halogens).

$$\begin{array}{|c|c|c|} \hline \text{Element} & \text{State at r.t.p.} & \text{Colour} \\ \hline \text{chlorine} & \text{gas} & \text{pale green} \\ \hline \text{bromine} & \text{liquid} & \text{red-brown} \\ \hline \text{iodine} & \text{solid} & \text{grey-black} \\ \hline \text{astatine} & X & Y \\ \hline \end{array}$$

Which row correctly identifies $X$ and $Y$?

Which reagent and observation can be used to distinguish between propane and propene?

An ion \(X^{2+}\) has 24 neutrons and 18 electrons. What is the nucleon number of element \(X\)?

Four gas jars containing different gases are placed upside down over gas jars containing air. Which gas will diffuse into the air the slowest?

Concentrated aqueous sodium bromide is electrolysed using inert carbon electrodes. Which row correctly describes the observations at each electrode?

The properties of four metals, W, X, Y and Z, are listed. Metal W reacts with steam but not with cold water. Metal X reacts violently with cold water. Metal Y does not react with dilute acid. Metal Z is obtained by heating its oxide with carbon. What is the correct order of reactivity of these metals, starting with the most reactive?

What volume of oxygen gas (measured at r.t.p.) is required for the complete combustion of 6.0 g of magnesium? [Relative atomic mass: \(\text{Mg} = 24\)]

A synthetic polymer has the repeating structure: \(-[- \text{O}-\text{CH}_2-\text{CH}_2-\text{O}-\text{CO}-\text{C}_6\text{H}_4-\text{CO} -]-\). Which pair of monomers is used to form this polymer?

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

Why does an increase in temperature increase the rate of a chemical reaction? 1. The particles collide more frequently. 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.

Carbon-14 is a radioactive isotope of carbon. It can be represented by the nuclide notation \(^{14}_{6}\text{C}\).\
\
(a) Complete the list to show the number of protons, neutrons, and electrons in one atom of carbon-14. [3]\
- Protons: \\dots\\dots\
- Neutrons: \\dots\\dots\
- Electrons: \\dots\\dots\
\
(b) Define the term isotopes. [2]\
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(c) State the electronic configuration of a neutral carbon-14 atom. [1]\
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(d) With reference to its electronic configuration, state the Group number of carbon in the Periodic Table and explain why it is placed in this Group. [2]\
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(e) Nitrogen-14 is in the same period as carbon. State the percentage of nitrogen gas present in clean, dry air. [2]

Water is an essential resource that undergoes treatment before domestic use.\
\
(a) Explain the purpose of the following steps in domestic water treatment:\
(i) filtration [1]\
(ii) chlorination [1]\
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(b) Describe a chemical test to show the presence of water, including the expected colour change. [2]\
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(c) State how a physical test can show if a sample of water is pure. [2]\
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(d) A student is given a solid mixture of insoluble barium sulfate and soluble sodium chloride. Describe how the student can obtain a pure, dry sample of solid barium sulfate from this mixture. [4]

A student carries out an acid-base titration to determine the concentration of a sodium hydroxide solution using dilute hydrochloric acid.\
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(a) Name the piece of apparatus used to:\
(i) measure exactly 25.0 cm³ of the sodium hydroxide solution into a conical flask. [1]\
(ii) add the hydrochloric acid gradually until the end-point is reached. [1]\
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(b) Methyl orange indicator is added to the sodium hydroxide in the conical flask.\
State the colour change of the indicator at the end-point. [2]\
from \\dots\\dots to \\dots\\dots\
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(c) Write the word equation for this neutralisation reaction. [2]\
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(d) During the reaction, the temperature of the mixture increases. State the type of energy change and explain your choice with reference to thermal energy. [2]\
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(e) In a separate experiment, 20.0 cm³ of hydrochloric acid of concentration 0.10 mol/dm³ is neutralised. Calculate the number of moles of hydrochloric acid used. [2]

Hydrated copper(II) sulfate crystals can be prepared by reacting insoluble copper(II) oxide with dilute sulfuric acid.\
\
(a) Explain why excess copper(II) oxide is added to the acid. [1]\
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(b) Describe how the unreacted copper(II) oxide is removed from the reaction mixture. [1]\
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(c) Describe how to obtain large, pure crystals of hydrated copper(II) sulfate from the resulting solution. [3]\
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(d) Copper(II) oxide is a basic oxide.\
(i) State what is meant by the term basic oxide with reference to its reaction with acids. [1]\
(ii) Give the chemical formula of an acidic oxide. [1]\
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(e) Complete the chemical equation for the reaction, including state symbols for all products.\
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\\text{CuO(s)} + \\text{H}_2\\text{SO}_4\\text{(aq)} \\rightarrow \\dots\\dots(\\dots\\dots) + \\dots\\dots(\\dots\\dots) [3]

Poly(ethene) is a common addition polymer used to make plastic bags.\
\
(a) Poly(ethene) is made from ethene monomers.\
(i) State the name of the feature in the ethene molecule that allows it to polymerise. [1]\
(ii) Complete the diagram to show the structure of poly(ethene) showing two repeating units. [2]\
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(b) Ethene is an unsaturated hydrocarbon.\
(i) Define the term hydrocarbon. [2]\
(ii) Describe a test to show that ethene is unsaturated, including the expected observations. [2]\
test: \\dots\\dots\
observation: \\dots\\dots\
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(c) State one environmental problem associated with the disposal of poly(ethene) in landfills and one alternative way to dispose of it. [3]

Molten lead(II) bromide is electrolysed using carbon (graphite) electrodes.\
\
(a) Explain why solid lead(II) bromide does not conduct electricity, but molten lead(II) bromide does. [2]\
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(b) State the observations at each electrode during the electrolysis of molten lead(II) bromide:\
(i) positive electrode (anode) [1]\
(ii) negative electrode (cathode) [1]\
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(c) Give two reasons why graphite is used for the electrodes. [2]\
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(d) When concentrated aqueous sodium chloride is electrolysed using inert electrodes:\
(i) Name the gas produced at the negative electrode (cathode). [1]\
(ii) Describe a test for this gas and the positive result. [2]\
test: \\dots\\dots\
result: \\dots\\dots\
(iii) State the name of the alkaline solution left behind in the cell. [1]

Chromatography and qualitative analysis tests are important chemical techniques.\
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(a) A student uses paper chromatography to separate the dyes in a green food coloring.\
(i) Explain why the starting line is drawn in pencil and not ink. [1]\
(ii) Define the term \(R_f\) value and write the formula used to calculate it. [2]\
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(b) An unknown white solid, X, is analysed.\
(i) A flame test is carried out on solid X. The flame is lilac.\
Identify the metal cation present in X. [1]\
(ii) Solid X is dissolved in water to make solution X. Dilute nitric acid and aqueous silver nitrate are added to solution X.\
A cream precipitate is formed.\
Identify the anion present in X. [2]\
(iii) State the chemical name and chemical formula of solid X. [2]\
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(c) Describe the test for chlorine gas and state the observation for a positive result. [2]\
test: \\dots\\dots\
result: \\dots\\dots

The reaction between magnesium and dilute hydrochloric acid is investigated.\
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\\text{Mg(s)} + 2\\text{HCl(aq)} \\rightarrow \\text{MgCl}_2\\text{(aq)} + \\text{H}_2\\text{(g)}\
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(a) Explain why the rate of reaction decreases as the reaction proceeds. [2]\
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(b) State two ways to increase the rate of this reaction without changing the concentration of the hydrochloric acid or using a catalyst. [2]\
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(c) This reaction can be classified as a redox reaction.\
(i) Define the term oxidation in terms of electron transfer. [1]\
(ii) Write the ionic equation for this reaction. [2]\
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(d) With reference to your ionic equation in (c)(ii):\
(i) Identify the species that is oxidised and explain your choice in terms of electron transfer. [2]\
(ii) Identify the oxidising agent. [1]