Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2024 Spring Zone 2

A list of substances is shown.
brass, calcium oxide, carbon monoxide, diamond, glucose, hydrogen, litmus, magnesium bromide, methyl orange, sodium chloride, stainless steel, thymolphthalein, water, zinc oxide.
Answer the following questions about these substances. Each substance may be used once, more than once or not at all.
(a) State which substance is formed by the thermal decomposition of calcium carbonate in the blast furnace.
(b) State which substance is a mixture of copper and zinc.
(c) State which substance turns yellow when an alkali is added.
(d) State which substance is a reactant in photosynthesis.
(e) State which substance is a salt that contains a positive ion with a charge of 1+.
(f) State which substance is a compound that reduces iron(III) oxide in the blast furnace.

(a) Answer these questions using the information in Table 2.1 [Table_1].
(i) Name the negative ion that has the highest concentration.
(ii) Name the compound that contains $\text{NH}_4^+$ and $\text{SO}_4^{2-}$ ions only.
(iii) Calculate the mass of hydrogencarbonate ions in 200 $\text{cm}^3$ of river water.
(b) Give a test for sodium ions.
Test ...
Observations ...
(c) Most of the nitrate ions in river water come from fertilisers used on fields. Describe the benefit of using fertilisers.
(d) Water from natural sources can be polluted with harmful substances. State why sewage and phosphates in river water are harmful.
Sewage ...
Phosphates ...
(e) River water can contain acids such as ethanoic acid and methylbutanoic acid.
(i) Draw the displayed formula for ethanoic acid.
(ii) Ethanoic acid reacts with sodium hydroxide. Complete the word equation for this reaction.
Ethanoic acid + Sodium hydroxide $\longrightarrow$ ...
(iii) Methylbutanoic acid has the molecular formula $\text{C}_5\text{H}_{10}\text{O}_2$. Complete Table 2.2 to calculate the relative molecular mass of $\text{C}_5\text{H}_{10}\text{O}_2$ [Table_2].

3 The chemical elements are arranged in the Periodic Table in groups and periods.
(a)(i) Describe how the metallic character of the elements changes from left to right across a period.
(ii) The elements in Group I are known as the alkali metals. Describe two trends in the properties of the elements, going down Group I.
1 ...
2 ...
(b) Chlorine, bromine and iodine are in Group VII of the Periodic Table.
(i) Aqueous chlorine reacts with aqueous sodium bromide to produce aqueous bromine and aqueous sodium chloride. Complete the symbol equation for this reaction.
$\text{Cl}_2 + ... \text{NaBr} \rightarrow ... + 2\text{NaCl}$
(ii) Suggest why aqueous iodine does not react with aqueous sodium bromide.
(iii) Complete the dot-and-cross diagram in Fig. 3.1 for a molecule of iodine . Show outer shell electrons only.
(c) Molten silver bromide is electrolysed using graphite electrodes. Name the product formed at each electrode.
Product at the anode ...
Product at the cathode ...
(d) Fig. 3.2 shows the apparatus used to electroplate a metal object with silver .
(i) Label Fig. 3.2 to show where the silver is deposited.
(ii) State why objects are electroplated.

4 Alkenes are a homologous series of hydrocarbons which are made by cracking larger alkane molecules.
(a)(i) Write the general formula for alkenes.
(ii) Explain the need for cracking larger alkane molecules.
(iii) Describe two conditions needed for cracking.
1 ...
2 ...
(b) Alkenes are unsaturated compounds. State the meaning of the term unsaturated.
(c) Table 4.1 shows the boiling points of some alkenes [Table_3].
(i) Predict the boiling point of propene.
(ii) The melting point of butene is $-185^\circ \text{C}$. Deduce the physical state of butene at $-100^\circ \text{C}$. Give a reason for your answer.
Physical state ...
Reason ...
(d) Fig. 4.1 shows a gas syringe that contains 60 $\text{cm}^3$ of ethene gas . State how the volume of ethene in the gas syringe changes when the temperature is decreased and the pressure remains the same.
(e) Poly(ethene) is produced by the polymerisation of ethene. The reaction is exothermic.
(i) State the meaning of the term exothermic.
(ii) Fig. 4.2 shows the reaction pathway diagram for this reaction . Explain how this reaction pathway diagram shows that the reaction is exothermic.
(f) Ethene reacts with steam to produce ethanol.
(i) Complete the symbol equation for this reaction.
$\text{C}_2\text{H}_4 + \text{steam} \rightarrow ...$
(ii) Choose the word which describes the type of catalyst used in this reaction. Draw a circle around your chosen answer.
acid alkali metal salt

5 Samarium is a metal.
(a) Deduce the number of electrons and neutrons in the samarium atom shown. $^{154}_{62}\text{Sm}$
Number of electrons ...
Number of neutrons ...
(b) Samarium has properties that are similar to the properties of transition elements. Choose one statement about samarium that is correct. Tick (✓) one box.
Compounds of samarium are colourless.
Samarium has a low melting point.
Samarium and its compounds do not act as catalysts.
Samarium has a high density.
(c) Large pieces of samarium react with cold water to produce hydrogen gas.
$2 \text{Sm} + 6 \text{H}_2\text{O} \rightarrow 2 \text{Sm(OH)}_3 + 3\text{H}_2$
(i) Complete Fig. 5.1 by drawing the apparatus to show how the volume of hydrogen gas is measured during this reaction .
(ii) The experiment is repeated using hot water instead of cold water. All other conditions stay the same. Describe how the rate of reaction changes when hot water is used.
(iii) The experiment is repeated using powdered samarium instead of large pieces of samarium. All other conditions stay the same. Describe how the rate of reaction changes when powdered samarium is used.
(d) Table 5.1 shows the observations when samarium and three other metals are heated in oxygen [Table_4]. Put the four metals in order of their reactivity. Put the least reactive metal first.
Least reactive ... Most reactive
(e) Samarium reacts with oxygen to produce samarium oxide, $\text{Sm}_2\text{O}_3$. Complete the symbol equation for this reaction.
$...\text{Sm} + 3\text{O}_2 \rightarrow ...\text{Sm}_2\text{O}_3$
(f) Hydrated samarium chloride is an ionic compound.
(i) Define the term hydrated.
(ii) State two physical properties of an ionic compound.
1 ...
2 ...

6 Sulfur is an element in Group VI of the Periodic Table.
(a) State the meaning of the term element.
(b) Sulfur has a relative atomic mass of 32. Complete these sentences about the relative atomic mass of sulfur using terms from the list.
12C electrons 1H isotopes neutrons 16O protons 32S
The relative atomic mass of sulfur is the average mass of the sulfur ...
This average mass is compared to 1/12th of the mass of an atom of ...
(c) Sulfur is a solid at room temperature and pressure. Describe the motion and separation of the particles in solid sulfur.
Motion ...
Separation ...
(d) Liquid sulfur reacts with chlorine to produce disulfur dichloride.
$2\text{S} + \text{Cl}_2 \rightarrow \text{S}_2\text{Cl}_2$
(i) Describe how the general physical properties of a liquid differ from those of a solid. Give two differences.
1 ...
2 ...
(ii) When 6.4g of sulfur reacts with excess chlorine, 13.5g of disulfur dichloride is produced. Calculate the mass of disulfur dichloride produced when 19.2 g of sulfur reacts with excess chlorine.
Mass = ... g
(e) Sulfur dioxide is formed when sulfur burns in air.
(i) State the percentage of oxygen in clean, dry air.
(ii) State one source of the pollutant sulfur dioxide in the air other than from burning sulfur.
(iii) State one adverse effect of sulfur dioxide in the air.
(iv) State one method of reducing the emissions of sulfur dioxide.
(v) Sulfur dioxide dissolves in water to form sulfurous acid. Give the formula of the ion that is present in all aqueous acids.
(vi) Sulfur dioxide reacts with oxygen in the presence of a catalyst to form sulfur trioxide. This is a reversible reaction. Complete the equation for this reaction by writing the sign for a reversible reaction in the box.
$2\text{SO}_2 + \text{O}_2 \rightleftharpoons 2\text{SO}_3$

7 Magnesium is an element in Group II of the Periodic Table.
(a) Deduce the electronic configuration of magnesium.
(b) Magnesium can be produced by reducing magnesium oxide with barium.
$\text{MgO} + \text{Ba} \rightarrow \text{Mg} + \text{BaO}$
Explain how this equation shows that magnesium oxide is reduced.
(c) Alloys of magnesium and aluminium are resistant to corrosion. Choose the diagram, A, B, C, or D, in Fig. 7.1 that best shows the structure of an alloy .
(d)(i) Complete the word equation for the reaction of magnesium oxide with hydrochloric acid.
Magnesium oxide + Hydrochloric acid $\rightarrow$ ...
(ii) Magnesium oxide is insoluble in water. Choose from the list one other compound that is insoluble in water. Tick (✓) one box.
magnesium carbonate
magnesium chloride
magnesium nitrate
magnesium sulfate
(e) Fig. 7.2 shows the electronic configuration of an element in Group II of the Periodic Table . Deduce the period in the Periodic Table to which this element belongs.