4CH1/2C — June 2022 (Edexcel IGCSE Chemistry): Past Paper

The box gives the names of some gases.

argon · carbon dioxide · hydrogen · nitrogen · oxygen · water vapour

Choose gases from the box to answer these questions.

Identify the least reactive gas in the atmosphere.

Identify the most abundant gas in the atmosphere.

Identify the gas that is not normally found in the atmosphere.

State an environmental problem caused by increasing amounts of carbon dioxide in the atmosphere.

Describe a test for carbon dioxide.

The diagram shows two pieces of apparatus, X and Y. cm³ 30 cm³ X Y

Give the name of each piece of apparatus. X Y

In a titration, a student adds 25.0 cm³ of barium hydroxide solution to a conical flask. Give a reason why it is better to use Y rather than X.

The student uses methyl orange indicator in the titration.

State the colour of methyl orange in barium hydroxide solution.

Give a reason why universal indicator is not suitable for use in a titration.

The student adds some dilute nitric acid to a burette and does the titration. The equation for the reaction is Ba(OH)₂ + 2HNO₃ → Ba(NO₃)₂ + 2H₂O The student finds that 21.50 cm³ of nitric acid of concentration 0.600 mol/dm³ neutralises 25.0 cm³ of barium hydroxide solution. Calculate the concentration, in mol/dm³, of the barium hydroxide solution. concentration = mol/dm³

State why sulfuric acid would not be a suitable acid to use in this titration.

This question is about Group 7, the halogens.

Which halogen has the palest colour?

Which halogen is a solid at room temperature?

The table shows the electronic configurations of a fluorine atom and a chlorine atom. Electronic configuration fluorine 2.7 chlorine 2.8.7 Explain the relative reactivities of fluorine and chlorine using the information in the table.

Lithium reacts with chlorine to form lithium chloride.

Write a chemical equation for the reaction of lithium with chlorine.

Describe tests to show that the product of the reaction is lithium chloride.

This question is about magnesium and magnesium compounds.

Magnesium burns in oxygen to form magnesium oxide. State two observations that would be seen during the reaction. 1 2

The diagram shows the electron configurations of a magnesium atom and an oxygen atom. magnesium atom oxygen atom Describe the changes in the electronic configurations when magnesium reacts with oxygen to form the ionic compound magnesium oxide, MgO

Magnesium can be produced by the electrolysis of molten magnesium chloride.

State why magnesium cannot be produced by heating magnesium oxide with carbon.

Explain the different ways that magnesium and magnesium chloride conduct electricity. magnesium magnesium chloride

During the electrolysis of molten magnesium chloride, magnesium is formed at the negative electrode. The ionic half‑equation for the reaction is Mg²⁺ + 2e– → Mg

State why this is a reduction reaction.

Write an ionic half‑equation for the formation of chlorine at the positive electrode.

An organic compound has this percentage composition by mass. C = 40 % H = 6.7 % O = 53.3 %

Show that the empirical formula of the compound is CH₂O

Draw the structural formula of a compound with the molecular formula C₂H₄O₂

Methanoic acid (HCOOH) reacts with sodium carbonate solution to give three products.

Complete the equation for this reaction. 2HCOOH + Na₂CO₃ → + +

State what you would observe in this reaction.

Methanoic acid also reacts with propanol to form an ester. The equation for the reaction is HCOOH + C₃H₇OH ⇌ HCOOC₃H₇ + H₂O

Give the name of the ester that forms.

State what is meant by the ⇌ symbol.

When this reaction occurs in a sealed container, the reaction can reach dynamic equilibrium. Give one characteristic of a reaction at dynamic equilibrium.

A polyester forms when butanedioic acid reacts with ethanediol. The diagram shows the repeat unit of the polyester that forms. O O C CH₂CH₂ C O CH₂CH₂ O

Give the name of this type of polymerisation.

Draw the structural formulae of the two monomers used to make this polyester.

Titanium is an important metal in industry. Titanium dioxide (TiO₂) can be converted into titanium metal in two stages. Stage 1 titanium dioxide is converted into titanium(IV) chloride (TiCl 4) Stage 2 titanium(IV) chloride is converted into titanium

This is the equation for the reaction in stage 1. TiO₂ + 2Cl₂ + C → TiCl₄ + CO₂ Calculate the volume, in dm³, of chlorine gas at rtp needed to react completely with 20 tonnes of titanium dioxide. Give your answer in standard form. [1 tonne = 106 g Mr of TiO₂ = 80] [molar volume of chlorine gas at rtp = 24 dm³] volume of chlorine gas = dm³

In stage 2, titanium(IV) chloride vapour is passed through molten magnesium in a container filled with argon. This is the equation for the reaction in stage 2. TiCl 4 + 2Mg → Ti + 2MgCl₂ Explain why the container is filled with argon rather than air.

Aeroplanes are made of an alloy containing aluminium and titanium. Explain why the alloy is stronger than pure titanium metal. You may include diagrams in your answer.

A student uses this apparatus to find the heat energy supplied by a liquid fuel. thermometer copper container water liquid fuel The student burns some fuel to heat the water in the copper container and measures the change in temperature.

The student notices that the bottom of the container turns black. Give the name of the black substance that forms on the bottom of the container.

In one experiment, the student burns 0.92 g of ethanol. The student calculates that the heat energy absorbed by the water is 18.2 kJ. Show that the results of this experiment give an approximate value for the enthalpy of combustion of ethanol of ΔH = –900 kJ/mol. [Mr of ethanol = 46]

The data book value of ΔH for the combustion of ethanol is –1367 kJ/mol. Give two reasons why the student’s value is much lower than the data book value. 1 2

The equation shows the combustion of methane. CH₄ + 2O₂ → CO₂ + 2H₂O ΔH = –890 kJ/mol This is the equation showing the displayed formulae. H O O H O H H C H + → O C O + O O H O H H The table shows the bond energies for O O, C O and O H

Calculate the bond energy of the C H bond, using information from the equation and the table. C H bond energy = kJ/mol

Complete the energy level diagram to show the products and ΔH. Energy CH₄ + 2O₂