4CH1/2C — January 2023 (Edexcel IGCSE Chemistry): Past Paper

The diagram shows the electronic configuration of an atom of an element. A Complete the table by giving the missing information. Name of the part of this atom labelled A Number of the group that contains this element Number of the period that contains this element

The table gives information about four different species, W, X, Y and Z. Species Number of protons Number of neutrons Number of electrons W 2 2 2 X 13 14 10 Y 17 18 17 Z 17 20 17

Give the mass number of W.

Give a reason why X has a 3+ charge.

Explain why Y and Z are isotopes of the same element.

The table shows properties of four substances, A, B, C and D

Use information from the table to identify these substances.

Which substance could be a metal? A B C D

Which substance could be diamond? A B C D

Which substance is a gas at 600 °C? A B C D

One of the substances in the table is a compound with the formula C₁₀H₁₆N₂O₃S

Give the number of different elements in C₁₀H₁₆N₂O₃S

Determine the number of atoms in a molecule of C₁₀H₁₆N₂O₃S

This question is about soluble salts and insoluble salts.

Which pair of solutions produces an insoluble salt when mixed?

When solutions of lead nitrate and sodium sulfate are mixed, one product is solid lead sulfate. This is the equation for the reaction. Pb(NO₃)₂(aq) + Na₂SO₄(aq) → PbSO₄(s) + 2NaNO₃(aq) Describe how a pure, dry sample of solid lead sulfate can be obtained from the mixture.

The table gives the solubility of a salt in water at six different temperatures. Temperature in °C 0 20 40 60 80 100 Solubility in g per 100 g of water 18 34 54 77 104 142

Plot the points on the grid.

Draw a curve of best fit. 160 140 120 100 Solubility in g per 100 g of water 0 20 40 60 80 100 Temperature in °C

A saturated solution of the salt in 100 g of water is cooled from 90 °C to 30 °C. Use your graph to determine the mass of salt that will crystallise. Show your working on the graph. mass of salt = g

The box shows the names of some fractions obtained from crude oil.

refinery gases · gasoline · kerosene · diesel · fuel oil · crude oil · bitumen

Describe how crude oil is separated into fractions in the fractionating column.

Give a use for kerosene and a use for bitumen. kerosene bitumen

Some fractions obtained from crude oil are cracked to form alkenes.

Describe what is meant by cracking.

Ethene is obtained by cracking. This is the displayed formula of ethene. H H C C H H Explain why ethene is described as an unsaturated hydrocarbon.

Describe a test to show that ethene is unsaturated.

This question is about metals.

Explain why metals are malleable.

Sodium metal is extracted by the electrolysis of molten sodium chloride. Sodium metal forms at the negative electrode and chlorine gas forms at the positive electrode. The diagram represents this electrolysis. positive electrode negative electrode molten sodium chloride

Explain why molten sodium chloride conducts electricity.

Explain how sodium metal forms at the negative electrode.

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

Give a reason why sodium metal does not form in the electrolysis of an aqueous solution of sodium chloride.

Copper can be produced by reacting an oxide of copper with methane. The diagram shows the apparatus used. excess methane burning methane gas oxide of copper in weighing boat heat The oxide of copper is heated until the reaction is complete. The table shows the results. Mass in g empty weighing boat 17.25 weighing boat + oxide of copper 22.02 weighing boat + copper 21.06 Use the results to show that this oxide has the empirical formula CuO [for Cu, A r = 63.5 for O, A r = 16]

When ethanoic acid reacts with ethanol in the presence of concentrated sulfuric acid, one of the products is ester A. This is the equation for the reaction

Draw a circle around the functional group in ethanoic acid.

Give the displayed formula of ester A.

Name ester A.

The reaction mixture is kept in a sealed container until dynamic equilibrium is reached. State what is meant by the term dynamic equilibrium.

During the reaction, the number of moles of ethanoic acid in the reaction mixture decreases, but the number of moles of concentrated sulfuric acid does not change.

Give a reason why the number of moles of concentrated sulfuric acid does not change.

A student does a titration to find the accurate volume of sodium hydroxide solution needed for complete neutralisation. The student starts by using a pipette to transfer 25.0 cm³ of the reaction mixture to a conical flask. Describe how the student should complete the titration.

This question is about hydrazine, N₂H₄

This is the displayed formula for a molecule of hydrazine. H H N N H H Complete the dot‑and‑cross diagram for hydrazine. H H N N H H

This is the equation for the decomposition of hydrazine. 3N₂H₄(g) → 4NH₃(g) + N₂(g) The equation can be shown using displayed formulae. H H N N N H H H H H N H H H H H N N + N N H H N H H H H H N N N H H H H H The table gives the relevant bond energies

Use the data in the table to calculate the total energy needed to break all the bonds in the reactants. energy needed = kJ

Use the data in the table to calculate the total energy released when all the bonds in the products are made. energy released = kJ

Calculate the enthalpy change, ΔH, in kJ/mol, for the reaction. ΔH = kJ/mol

Explain, in terms of bonds broken and bonds made, why this reaction is exothermic.

A sample of hydrazine is completely decomposed. This is the equation for the decomposition of hydrazine. 3N₂H₄(g) → 4NH₃(g) + N₂(g) The products of the decomposition are bubbled through 1100 cm³ of water. The ammonia completely dissolves in the water, but nitrogen is insoluble in water. The nitrogen has a volume of 1570 cm³ at room temperature and pressure (rtp). Calculate the concentration, in mol/dm³, of the ammonia solution. Give your answer to 3 significant figures. [for a gas at rtp, molar volume = 24 000 cm³ ] concentration = mol/dm³