4CH1/2C — November 2021 (Edexcel IGCSE Chemistry): Past Paper

Use the Periodic Table to help you answer this question.

Identify the element with atomic number 7

Identify a solid non‑metallic element in Period 3

Name an element in Group 7 that is a liquid at room temperature.

State the relative atomic mass of the element that is in Group 4 and Period 4

Which row shows the most reactive element in Group 1 and Group 7? Most reactive element Most reactive element in Group 1 in Group 7

The box lists words that may be used to explain the term saturated solution. solute solvent temperature Explain, using all the words in the box, the term saturated solution.

The diagram shows the apparatus a student uses to make a saturated solution. thermometer water solid heat This is the student’s method. Step 1 add 4.5 g of solid to a boiling tube Step 2 measure exactly 10.0 cm³ of pure water and pour into the boiling tube Step 3 place the boiling tube in the beaker of water and heat gently, stirring the mixture continuously until all the solid dissolves Step 4 remove the boiling tube from the beaker and allow it to cool Step 5 record the temperature when crystals start to form in the boiling tube The recorded temperature shows when the solution becomes saturated.

Name the piece of apparatus that the student should use in Step 2 to measure exactly 10.0 cm³ of pure water.

Suggest why the boiling tube is not heated directly using a Bunsen burner in Step 3.

Suggest how the student could improve the reliability of her recorded temperature in Step 5.

In Step 5, crystals start to form at 26 °C. Calculate the solubility of the solid, in g per 100 g of water, at 26 °C. [1.0 cm³ of pure water has a mass of 1.0 g] solubility = g per 100 g of water

The solubility curves for two solids, A and B, are shown on the grid. 300 280 260 A 240 220 200 180 B 160 Solubility in g per 100 g water 140 120 100 20 30 40 50 60 70 80 90 100 Temperature in °C

State the temperature when A and B have the same solubility. temperature = °C

Calculate the mass of B that will dissolve in 250 g of water at 60 °C. Show your working. mass = g

Suggest why the values for the solubility of A and B may be less accurate at 95 °C than at lower temperatures.

Sulfur dioxide (SO₂) and hydrogen sulfide (H₂S) are both gases. The two gases react together to form solid sulfur and water.

Complete the chemical equation for the reaction. 2H₂S( ) + SO₂( ) → S(s) + H₂O( )

State why the sulfur dioxide is reduced in the reaction.

The diagram shows apparatus used to compare the speed at which particles of the two gases diffuse. cotton wool soaked in pale yellow cotton wool soaked in sulfur dioxide solution solid hydrogen sulfide solution rubber rubber bung bung The two pieces of cotton wool and rubber bungs are put in position at the same time. A pale yellow solid soon forms.

Explain how the diagram shows that hydrogen sulfide gas diffuses more quickly than sulfur dioxide gas.

Deduce a relationship between the relative formula mass (Mr) of a gas and the speed at which a gas diffuses. Use the Ar values to help you. [Ar values: H = 1 S = 32 O = 16]

This question is about ionic compounds.

State the formula of the cation and the anion in magnesium sulfate. cation anion

The diagram shows the electronic configuration of a potassium atom and an oxygen atom. potassium oxygen Potassium oxide (K₂O) is an ionic compound. Draw the electronic configuration of a potassium ion and an oxide ion. Show the charge on each ion. potassium ion oxide ion

A sample of solid potassium oxide is added to water. A reaction occurs and a colourless solution forms. When a few drops of phenolphthalein indicator are added to the solution it turns pink.

Identify the ion responsible for the colour change.

Give a chemical equation for the reaction between potassium oxide and water.

Explain why ionic compounds conduct electricity when molten or in aqueous solution, but not when in the solid state.

The diagram shows the apparatus a teacher uses to demonstrate the electrolysis of a concentrated aqueous solution of sodium chloride. gas X gas Y sodium chloride solution inert electrodes + − During the electrolysis two gases, X and Y, are formed. One of the gases produces a squeaky pop when tested with a lighted splint. Use ionic half‑equations to identify X and Y.

Metals are found in the Earth's crust either as uncombined elements or in metal compounds in rocks. The method of extraction of a metal is related to its position in the reactivity series. The table shows the positions of some metals and carbon in the reactivity series.

most reactive potassium · sodium · lithium · calcium · magnesium · aluminium · carbon · zinc · iron · lead · copper · silver · gold least reactive platinum

State the name given to rocks that contain metal compounds used in the extraction of metals.

Name a metal that is found as an uncombined element in the Earth’s crust.

Carbon extraction and electrolysis are two methods of obtaining a metal from a compound.

Explain, without giving practical details, which method is most suitable to obtain calcium from calcium chloride.

Explain, without giving practical details, which method is most suitable to obtain lead from lead oxide.

Explain, using a labelled diagram, why lead metal is malleable.

No printed figure accompanies this part — in the paper you would draw the diagram (or label the apparatus) in the answer space provided.

Aluminium is extracted from aluminium oxide. The overall equation for the process is 2Al₂O₃ → 4Al + 3O₂ Calculate the maximum mass, in grams, of aluminium that could be obtained from 1.275 kg of aluminium oxide. mass = g

This question is about alcohols, carboxylic acids and esters.

Ethanol can be manufactured by reacting ethene with steam in the presence of a phosphoric acid catalyst. Which row gives the correct conditions of temperature and pressure for this reaction? Temperature in °C Pressure in atmospheres

Give the displayed formula of butanol.

Ethanoic acid (CH₃COOH) is a carboxylic acid present in vinegar.

The concentration of CH₃COOH in vinegar can be found by titration with aqueous potassium hydroxide (KOH). The equation for the reaction is CH₃COOH + KOH → CH₃COOK + H₂O In a titration, a 25.0 cm³ sample of vinegar is neutralised by 45.00 cm³ of KOH solution of concentration 0.400 mol/dm³. Calculate the concentration, in mol/dm³, of CH₃COOH in this sample of vinegar. concentration = mol/dm³

A sample of vinegar containing 0.0030 mol of CH₃COOH is poured into a flask. Calculate the maximum volume, in cm³, of carbon dioxide gas formed at rtp when excess sodium carbonate is added to the flask. The equation for the reaction is 2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂ [Assume that the molar volume of carbon dioxide at rtp is 24 000 cm³] volume = cm³

Alcohols react with carboxylic acids to form esters. Which alcohol could react to form the ester ethyl propanoate?

Polyesters are formed in condensation polymerisation reactions between dicarboxylic acids and diols.

State one difference between condensation polymerisation and addition polymerisation.

The repeat unit of a polyester is Give the displayed formula of each of the two monomers needed to form this polyester.

Give one advantage of biopolyesters.

Hydrogen gas and iodine gas react together to form hydrogen iodide gas. H₂(g) + I₂(g) ⇌ 2HI(g)

The pressure of an equilibrium mixture of the three gases is increased. Predict the effect of this change on the yield of hydrogen iodide at equilibrium, giving a reason for your answer.

A catalyst is added to an equilibrium mixture of the three gases. Predict the effect of the catalyst on the yield of hydrogen iodide at equilibrium, giving a reason for your answer.

Hydrogen gas reacts with fluorine gas to form hydrogen fluoride gas. H₂(g) + F₂(g) → 2HF(g) The table gives some bond energies. Bond Bond energy in kJ/mol H H 436 F F 158 H F 562 Use the equation and the data in the table to calculate the enthalpy change (ΔH) in kJ/mol, for the reaction. Include a sign in your answer. ΔH = kJ/mol

Draw an energy level diagram for the reaction between hydrogen and fluorine. Label the enthalpy change, ΔH. Energy