IGCSE Chemistry 0620 Paper 33, Oct/Nov 2025

is used in food containers because of its resistance to corrosion

is a metal that does not react with water, dilute acids or oxygen

reacts with hydrogen in a fuel cell

is bonded to hydrogen in methane.

Complete Table 2.1 to show the number of neutrons and nucleons in one atom of ${}_{54}^{131}\mathrm{X}\mathrm{e}$. Table 2.1

Xenon is a gas at room temperature and pressure. A sample of xenon is placed in a sealed syringe with a freely moving plunger. Complete Table 2.2 to show the effect, if any, on the volume of xenon when: • the temperature of the xenon is decreased • the pressure of the xenon is decreased. Use the words increases, decreases or no change in your answer. Table 2.2

When xenon is cooled, it becomes a solid. Describe the arrangement and motion of the particles in solid xenon. particle arrangement particle motion

Table 3.1 shows the masses of ions, in $\mathrm{m}\mathrm{g}$, present in a $600{\mathrm{c}\mathrm{m}}^3$ sample of contaminated water. Table 3.1

Answer these questions using the information from Table 3.1. Name the positive ion that has the highest concentration.

State the name of the ${\mathrm{P}\mathrm{O}}_4^{3-}$ ion.

Describe a test to identify the presence of nitrate ions, ${\mathrm{N}\mathrm{O}}_3^{-}$, in a sample of water. test test result

Calculate the mass of sodium ions, ${\mathrm{N}\mathrm{a}}^{+}$, in $200{\mathrm{c}\mathrm{m}}^3$ of the contaminated water. $$\text{mass}=\text{..............................}\mathrm{m}\mathrm{g}$$

A higher concentration of nitrate ions in river water can cause deoxygenation. State a source of a higher concentration of nitrate ions in river water.

A sample of water is taken from a river. The sample contains some insoluble substances. State one method of removing the insoluble substances from the water.

The water contains harmful microbes. Suggest a source of the microbes in the water.

State how the water is treated so that the microbes do not cause harm to people.

Before the treatment in (c)(ii), the water has a bad taste and odour. State the name of a substance that is added to remove the bad taste and odour from the water.

Compound B is a molecule found in a plant called basil. Fig. 4.1 shows the displayed formula of a molecule of compound B. Fig. 4.1 Deduce the molecular formula of compound B to show the number of atoms of carbon, hydrogen and oxygen.

On Fig. 4.1, draw a circle around one part of the molecule which shows that the molecule is unsaturated.

A different molecule found in plants has the molecular formula ${\mathrm{C}}_9{\mathrm{H}}_{10}{\mathrm{O}}_3$. Complete Table 4.1 to calculate the relative molecular mass of ${\mathrm{C}}_9{\mathrm{H}}_{10}{\mathrm{O}}_3$. Table 4.1

$$\text{relative molecular mass}=\text{..............................}$$

Fig. 4.2 shows the names of some of the fractions obtained from petroleum using a fractionating column. Fig. 4.2 Using only the fractions shown in Fig. 4.2, name the fraction which contains compounds that: have the highest boiling point

Using only the fractions shown in Fig. 4.2, name the fraction which contains compounds that: have the shortest chain length

Using only the fractions shown in Fig. 4.2, name the fraction which contains compounds that: are used to make waxes and polishes.

Table 4.2 shows some properties of alcohols. Table 4.2

The compounds in Table 4.2 are members of the alcohol homologous series. State what is meant by the term homologous series.

A molecule of octanol has eight carbon atoms. Use the information in Table 4.2 to deduce the formula of octanol.

Use the information in Table 4.2 to predict the melting point of nonanol.

Hexanol is a fuel. In excess oxygen, hexanol undergoes complete combustion to produce water and one other product. Identify this other product.

State the colour change observed when water is added to anhydrous copper(II) sulfate. from white to ..............................

Ethanol can be manufactured by fermentation. Name the reactant, and state two conditions needed for the fermentation of ethanol. reactant condition 1 condition 2

Ethanol can be converted into ethanoic acid. Draw the displayed formula of ethanoic acid. Show all the atoms and all the bonds.

Silicon is in Group IV of the Periodic Table. Explain why silicon is placed in Group IV. Give your answer in terms of electronic configuration.

Tin is also in Group IV of the Periodic Table. Table 5.1 shows the melting point and the boiling point of tin. Table 5.1

Use Table 5.1 to deduce the physical state of tin at 175°C. Give a reason for your answer. physical state reason

Iodine is in Group VII of the Periodic Table. Give the colour and state of iodine at room temperature and pressure. colour state

When a sample of calcium is added to a large container of cold water, a chemical reaction occurs. Describe what is observed when calcium is added to water.

Complete the word equation for the reaction of calcium with water. $$\text{calcium}+\text{water}\to \text{....................}+\text{....................}$$

Dilute nitric acid is poured into a conical flask. Choose the pH value of dilute nitric acid. Draw a circle around your chosen answer. $$\text{pH}\text{1}\text{pH}\text{7}\text{pH}\text{9}\text{pH}\text{13}$$

Complete the equation for the neutralisation of an acid to produce water. State symbols are not required. $${\mathrm{H}}^{+}+\text{....................}\to {\mathrm{H}}_2\mathrm{O}$$

A few drops of methyl orange indicator are added to the flask containing dilute nitric acid. Solid lithium carbonate is slowly added to the flask until the indicator changes colour. State the colour change of the methyl orange indicator as the lithium carbonate is added to the dilute nitric acid in the flask. $$\text{from ............................................................. to .............................................................}$$

Lithium carbonate reacts with dilute nitric acid to form aqueous lithium nitrate. Describe a test to show that ${\mathrm{L}\mathrm{i}}^{+}$ ions are present in the solution. test observations

Chlorine is in Group VII of the Periodic Table. Chlorine reacts with lithium to form the ionic compound lithium chloride. Complete the dot-and-cross diagram in Fig. 5.1 for lithium chloride to show: • the electronic configuration for each ion • the charge on each ion. Use crosses to represent the electrons of lithium. Fig. 5.1

Iron is extracted from its ore using carbon in a blast furnace. When calcium carbonate is heated strongly in the blast furnace, it forms calcium oxide and carbon dioxide. $${\mathrm{C}\mathrm{a}\mathrm{C}\mathrm{O}}_3\to \mathrm{C}\mathrm{a}\mathrm{O}+{\mathrm{C}\mathrm{O}}_2$$ State the type of reaction that occurs when calcium carbonate is heated strongly.

State whether calcium oxide is an acidic oxide or a basic oxide. Explain your answer.

Name the gas removed by calcium oxide in flue gas desulfurisation.

Zinc is also extracted from its ore using carbon. The equation for the extraction of zinc from zinc oxide is shown. $$2\mathrm{Z}\mathrm{n}\mathrm{O}+\mathrm{C}\to 2\mathrm{Z}\mathrm{n}+{\mathrm{C}\mathrm{O}}_2$$ Explain how this equation shows that zinc oxide is reduced.

Brass is an alloy that contains zinc. Name the other metal in brass.

Suggest two reasons why brass is used to make water taps rather than pure zinc. 1 2

The extraction of zinc from its ore produces atmospheric sulfur dioxide and carbon dioxide. State the adverse effect that increased levels of sulfur dioxide have on the environment.

Increased levels of carbon dioxide in the atmosphere can lead to increased global warming. State one strategy which would help to remove carbon dioxide that is already in the atmosphere.

Table 6.1 shows the observations when four different metals are added separately to dilute hydrochloric acid. Table 6.1

Put the four metals in order of their reactivity. Put the least reactive metal first.

Fig. 7.1 shows the apparatus used to electroplate a nickel object with copper. Fig. 7.1 Label the anode in Fig. 7.1.

Name a suitable aqueous electrolyte for the electroplating in Fig. 7.1.

Fig. 7.2 shows the apparatus used to electrolyse molten lead(II) bromide using inert electrodes. Fig. 7.2 State the colour of the gas produced at the anode in this electrolysis.

State whether the electrolysis of molten lead(II) bromide produces a physical or chemical change. Explain your answer. type of change explanation

Cobalt is a metal that reacts slowly with a dilute acid to produce cobalt(II) ethanoate and hydrogen. Name the dilute acid.

Describe a test for hydrogen. test observations

Cobalt(II) chloride, ${\mathrm{C}\mathrm{o}\mathrm{C}\mathrm{l}}_2$, exists in different forms. Draw one line from each form of cobalt(II) chloride to its description.

Give the meaning of the symbol (l) in the equation.

Fig. 8.1 shows the total volume of carbon dioxide gas, ${\mathrm{C}\mathrm{O}}_2$, produced as the reaction proceeds. Fig. 8.1 Use Fig. 8.1 to determine the total volume of ${\mathrm{C}\mathrm{O}}_2$ produced at $24\mathrm{s}$. $$\text{total volume of }{\mathrm{C}\mathrm{O}}_2\text{ at }24\mathrm{s}=\text{....................................................}{\mathrm{c}\mathrm{m}}^3$$

The reaction is repeated using excess citric acid of a lower concentration. All other conditions stay the same. State the effect, if any, on: the time taken for the reaction to finish

State the effect, if any, on: the total volume of ${\mathrm{C}\mathrm{O}}_2$ produced when the reaction is complete.

Fig. 8.2 shows the reaction pathway diagram for the reaction of dilute citric acid with aqueous sodium hydrogencarbonate. Fig. 8.2 Deduce the type of energy change shown in the diagram in Fig. 8.2. Explain your answer.