Edexcel IGCSE Chemistry Chemistry Paper 2 November 2024 question paper 4CH1/2C

The table shows the composition of five species that are either atoms or ions.

Use the table to answer these questions.

You may use each letter once, more than once, or not at all.

Give the letter of the species that is a negative ion.

Give the letter of the species that has a full outer shell of electrons.

Give the letter of the species that has an atomic number equal to its mass number.

Explain why species B and C are atoms of the same element with identical chemical properties.

A proton has a mass of 1.672610^–24g.

A neutron has a mass of 1.674010^–24g.

Calculate the mass, in grams, of the nucleus of an atom of species C.

This question is about metals and metal compounds.

All metals are malleable and good conductors of electricity.

The diagram shows the structure of a metal.

Explain why metals are malleable.

Explain why metals are good conductors of electricity.

Two methods of obtaining a metal from a compound are electrolysis and extraction using carbon.

Explain, without giving practical details, which method is most suitable for extracting iron from iron(III) oxide.

A student has a solution of iron(II) sulfate and a solution of iron(III) sulfate.

Describe a chemical test the student could use to identify which solution is iron(II) sulfate.

A teacher uses this apparatus to separate a mixture of ethanol and water.

Give the name of this method of separation.

Name the pieces of apparatus labelled X, Y and Z.

Give a physical test that the teacher could do to find out if the ethanol produced is pure.

A teacher adds a small piece of lithium to water and collects the gas produced.

Give two observations when lithium is added to water.

The teacher adds a few drops of universal indicator to the solution at the end of the reaction.

Explain the final colour of the universal indicator.

This is the equation for the reaction between lithium and water.

The teacher collects 550 cm³ of hydrogen at rtp.

Calculate the mass, in grams, of lithium that the teacher added to the water.

[one mole of gas at rtp has a volume of 24 000 cm³]

[for lithium, A_r = 7]

[for carbon A_r = 12 for hydrogen, A_r = 1 for oxygen A_r = 16]

The teacher then adds a small piece of potassium to water.

Give one observation seen with potassium that is not seen with lithium.

Explain why potassium is more reactive than lithium.

Refer to atomic structure in your answer.

A student does some titrations to find the volume of dilute nitric acid needed to exactly neutralise 25.0 cm³ of sodium hydroxide solution.

This is the student’s method.

Step 1 add 25.0 cm³ of sodium hydroxide solution to a conical flask

Step 2 add three drops of methyl orange indicator

Step 3 fill a burette with the acid

Step 4 add acid from the burette until the indicator changes colour

Step 5 record the volume of acid added

Give the name of the apparatus that the student should use to measure the volume of sodium hydroxide solution in step 1.

Give the colour change seen in step 4.

Give a reason why the student does not use universal indicator in this titration.

The student completes a rough titration and four accurate titrations.

The diagram shows the burette readings from the rough titration.

The table shows the student’s results.

Complete the table by adding the results from the rough titration.

Record the volumes to the nearest 0.05 cm³

Concordant results are results within 0.20 cm³ of each other.

Use the concordant results from the table to calculate the mean volume of acid added.

This is the equation for the reaction between dilute nitric acid and sodium hydroxide solution.

HNO₃(aq) + NaOH(aq) NaNO₃(aq) + H₂O(l)

After the titration, the student knows the volume of acid needed to neutralise 25.0 cm³ of the sodium hydroxide solution.

Sodium nitrate decomposes at high temperatures.

Describe how the student could obtain pure, dry crystals of sodium nitrate from dilute nitric acid and sodium hydroxide solution.

This question is about crude oil.

Describe how crude oil is separated into fractions by fractional distillation.

Some of the long-chain alkanes obtained from fractional distillation are cracked, producing shorter-chain alkanes and ethene.

Give the conditions necessary for cracking to occur.

Explain why shorter-chain alkanes are more useful than longer-chain alkanes.

Ethene reacts with bromine.

The equation shows the displayed formulae of the reactants and product.

H H

Br Br

The table shows some bond energies.

Show that the molar enthalpy change, Δ H, for this reaction is about –100 kJ/mol.

ΔH =_........ kJ/mol

Explain why the reaction between ethene and bromine is exothermic.

Refer to bond energies in your answer.

This question is about alcohols and carboxylic acids.

These are the structural formulae of alcohol A and carboxylic acid B.

Alcohol A
CH₃CH₂CH₂OH

Carboxylic acid B CH₃(CH₂)_nCOOH

Name alcohol A.

Draw the displayed formula of alcohol A.

Carboxylic acid B has a chain of carbon atoms with no branches.

The number of CH₂ units is represented by the letter n.

Calculate the value of n.

[for carboxylic acid B, M_r = 242]

Alcohol A and carboxylic acid B react together to form an ester.

Give the other product of the reaction.

These are the structural formulae of dicarboxylic acid C and diol D.

Dicarboxylic acid C HOOCCH₂CH₂COOH

Diol D
HOCH₂CH₂OH

This is the equation for the reaction between dicarboxylic acid C and sodium hydroxide solution.

HOOCCH₂CH₂COOH + 2NaOH NaOOCH₂CH₂COONa + 2H₂O

25.0 cm³ of 0.150 mol/dm³ sodium hydroxide solution is completely neutralised by 17.5 cm³ of a solution of dicarboxylic acid C.

Calculate the concentration, in mol/dm³, of the solution of dicarboxylic acid C.

Give your answer to three significant figures.

concentration =_........ mol/dm

Dicarboxylic acid C and diol D react to form a polyester.

Draw the displayed formula of the repeat unit of this polyester.