IGCSE Chemistry 0620 Paper 32, May/June 2023

forms 21% by volume of clean, dry air

has an atom with only three occupied electron shells

has an atom with only one electron in its outer shell

is a grey-black solid at room temperature

forms an ion that gives a green precipitate on addition of aqueous ammonia

is used in electrical wiring because of its good ductility.

Table 2.1 shows some properties of the halogens. Table 2.1 Use the information in Table 2.1 to predict: (i) the boiling point of iodine

the density of astatine at room temperature and pressure

the physical state of bromine at $+50{}^{\circ }\mathrm{C}$. Give a reason for your answer. physical state ...................................................................................................................... reason .................................................................................................................................

Aqueous bromine reacts with aqueous potassium iodide. (i) Complete the word equation for this reaction. $$\text{bromine}+\begin{array}{c}\text{potassium}\\ \text{iodide}\end{array}\to \dots \dots \dots \dots \dots \dots \dots \cdots +\dots \dots \dots \dots \dots \dots \dots \dots$$

Explain why aqueous iodine does not react with aqueous potassium bromide.

Describe a test for iodide ions. test ...................................................................................................................................... observations .......................................................................................................................

Water from natural sources can contain metal compounds and phosphates. (i) Name two other substances found in water which are harmful to aquatic life. 1 .......................................................................................................................................... 2 ..........................................................................................................................................

State why phosphates are harmful to aquatic life.

Table 3.1 shows the masses of ions, in $\mathrm{m}\mathrm{g}$, present in a $1000{\mathrm{c}\mathrm{m}}^3$ sample of polluted water. Answer these questions using information from Table 3.1. (i) Name the positive ion present in the highest concentration.

State the name of the ${\mathrm{N}\mathrm{O}}_3^{-}$ ion.

Calculate the mass of magnesium ions present in $250{\mathrm{c}\mathrm{m}}^3$ of polluted water. $$\text{mass}=\dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \mathrm{m}\mathrm{g}$$

Water is produced when blue copper(II) sulfate is heated. (i) Describe how white copper(II) sulfate can be changed to blue copper(II) sulfate.

Choose a word from the list which best describes white copper(II) sulfate. Draw a circle around your chosen answer. anhydrous aqueous hydrated oxidised

Complete the symbol equation for the reaction of calcium with water. $$\mathrm{C}\mathrm{a}+\dots \dots {\mathrm{H}}_2\mathrm{O}\to {\mathrm{C}\mathrm{a}(\mathrm{O}\mathrm{H})}_2+\dots \dots \dots \dots \dots \dots$$

Chlorine has diatomic molecules. Define the term diatomic.

Deduce the number of protons, neutrons and electrons in the chloride ion shown. $${}_{17}^{37}{\mathrm{C}\mathrm{l}}^{-}$$ number of protons ..................................................................................................................... number of neutrons ................................................................................................................... number of electrons ...................................................................................................................

Chlorine reacts with hydrogen to produce hydrogen chloride. The reaction is exothermic. (i) State the meaning of the term exothermic.

Fig. 4.1 shows an incomplete reaction pathway diagram for the reaction of chlorine with hydrogen. Complete Fig. 4.1 by writing these formulae on the diagram: ● ${\mathrm{C}\mathrm{l}}_2+{\mathrm{H}}_2$ ● $2\mathrm{H}\mathrm{C}\mathrm{l}$.

Explain how Fig. 4.1 shows that the reaction is exothermic.

A few drops of methyl orange indicator are added to dilute hydrochloric acid. State the colour of the solution.

Dilute hydrochloric acid reacts with sodium hydroxide. (i) Complete the word equation for this reaction. $$\begin{array}{c}\text{hydrochloric}\\ \text{acid}\end{array}+\begin{array}{c}\text{sodium}\\ \text{hydroxide}\end{array}\to \dots \dots \dots \dots \dots \dots \dots \cdots +\dots \dots \dots \dots \dots \dots \dots \dots$$

Sodium hydroxide is an alkali. Write the formula of the ion present in all alkalis.

Fig. 4.2 shows the apparatus used for the electrolysis of concentrated aqueous sodium chloride using graphite electrodes. Label Fig. 4.2 to show: ● the anode ● the electrolyte.

Name the products and state the observations at the positive and negative electrodes. product at the positive electrode ............................................................................................................................................. observations at the positive electrode ............................................................................................................................................. product at the negative electrode ............................................................................................................................................. observations at the negative electrode .............................................................................................................................................

Carbon is used to extract iron from iron ore in a blast furnace. (i) Name the main ore of iron.

Iron(III) oxide in the iron ore is reduced by carbon monoxide. Name the two substances which react in the blast furnace to produce carbon monoxide. ................................................................ and ................................................................

Iron rusts in the presence of oxygen and water. State one method of preventing rusting.

Table 5.1 shows some information about the reaction of four metals with steam. Table 5.1 Put the four metals in order of their reactivity. Put the least reactive metal first.

A student investigates the reaction of different-sized pieces of calcium carbonate with dilute hydrochloric acid. The sizes of the pieces of calcium carbonate are: ● large ● medium ● small. All other conditions stay the same. Table 6.1 shows the time taken for each reaction to finish. Table 6.1 (i) Complete Table 6.1 by writing the sizes of the pieces of calcium carbonate in the first column.

Describe the effect on the time taken for small pieces of calcium carbonate to finish reacting with dilute hydrochloric acid when the temperature is increased. All other conditions stay the same.

Describe the effect on the time taken for small pieces of calcium carbonate to finish reacting with dilute hydrochloric acid when the concentration of hydrochloric acid is decreased. All other conditions stay the same.

Crystals of calcium chloride can be prepared by reacting excess calcium carbonate with dilute hydrochloric acid. Name the process used to separate the unreacted calcium carbonate from the rest of the reaction mixture.

Calcium carbonate is insoluble in water. Choose one other compound that is insoluble in water. Tick (✓) one box. ammonium sulfate potassium nitrate silver chloride sodium hydroxide

Fig. 7.1 shows the displayed formula of compound D. (i) On Fig. 7.1 draw a circle around the alcohol functional group.

Deduce the molecular formula of compound D.

Explain, by referring to the structure in Fig. 7.1, why compound D is unsaturated.

Ethene is also an unsaturated compound. (i) Draw the displayed formula of ethene.

Describe a test for unsaturated compounds. test ...................................................................................................................................... observations .......................................................................................................................

Ethene can be manufactured by cracking larger alkane molecules. (i) State two conditions for cracking. 1 .......................................................................................................................................... 2 ..........................................................................................................................................

Complete the symbol equation for the cracking of decane, ${\mathrm{C}}_{10}{\mathrm{H}}_{22}$, to produce ethene and one other hydrocarbon. $${\mathrm{C}}_{10}{\mathrm{H}}_{22}\to {\mathrm{C}}_2{\mathrm{H}}_4+\dots \dots \dots \dots \dots \dots$$

Ethanol can be manufactured by the reaction of ethene with steam. Name one other method of manufacturing ethanol.

Ethanol can be oxidised to ethanoic acid. Ethanoic acid reacts with sodium. Name the salt formed when ethanoic acid reacts with sodium.

Ethanoic acid reacts with propanol. The organic product has the molecular formula ${\mathrm{C}}_5{\mathrm{H}}_{10}{\mathrm{O}}_2$. Complete Table 7.1 to calculate the relative molecular mass of ${\mathrm{C}}_5{\mathrm{H}}_{10}{\mathrm{O}}_2$. Table 7.1 $$\text{relative molecular mass}=\dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots \dots$$

Describe two physical properties which are typical of non-metals. 1 ................................................................................................................................................. 2 .................................................................................................................................................

Methane is a compound of carbon and hydrogen. (i) Complete Fig. 8.1 to show the dot-and-cross diagram for a molecule of methane. Show outer shell electrons only.

Methane is an alkane. Write the general formula for alkanes.

Methane is an air pollutant. State one source of methane in the air.

State one adverse effect of methane in the air.

Carbon particulates and water are two of the products of the incomplete combustion of methane. Name one other compound formed during the incomplete combustion of methane.

Sulfur dioxide is an air pollutant which contributes to acid rain. (i) Choose from the list the pH value that is acidic. Draw a circle around your chosen answer. pH 4 pH 7 pH 9 pH 13

State two methods of reducing acid rain. 1 .......................................................................................................................................... 2 ..........................................................................................................................................

Sulfur dioxide gas turns aqueous acidified potassium manganate(VII) from purple to colourless. Fig. 8.2 shows a gas jar of sulfur dioxide separated from a gas jar of air by a glass plate. A piece of filter paper soaked in aqueous acidified potassium manganate(VII) is glued to the top of the gas jar of air. The glass plate is removed. At first, the filter paper remains purple. After a short time, the filter paper turns colourless. Explain these results in terms of the kinetic particle theory.