4CH1/2C — November 2025 (Edexcel IGCSE Chemistry): Past Paper

The diagram shows some pieces of apparatus that can be used for different processes. The pieces of apparatus are not to scale

Complete the table by placing ticks (✓) in each column to show if a piece of apparatus can be used for a process. One tick has been done for you. Each piece of apparatus can be used for one process, more than one process, or not at all. Process Letter measures different evaporates solvent to titration volumes produce crystals P Q ü R S T U

Give the letter for the piece of apparatus that is a burette.

Name the piece of apparatus labelled R.

This question is about the halogens.

The table lists some halogens and their properties. Complete the table by giving the missing information. Halogen State at 25°C Colour fluorine pale yellow chlorine gas bromine brown iodine solid dark grey

Suggest the state of astatine at 25 °C.

A sample of bromine atoms contains 42.0% bromine‑79 and 58.0% bromine‑81. Calculate the relative atomic mass of this sample of bromine atoms. Give your answer to three significant figures. relative atomic mass =

A sample of chlorine contains 0.75 mol of 35Cl atoms and 0.25 mol of 37Cl atoms. The table gives the relative molecular masses (Mr) of the different diatomic molecules of chlorine. The table also gives the probability of having a molecule of 37Cl37Cl in this sample. Molecule Cl35Cl 35 Cl37Cl and 37Cl35Cl 37 Cl37Cl Mr 70 72 74 Probability 0.25 × 0.25 = 0.0625

Calculate the probability of having a molecule with an Mr of 70 probability =

Explain why the probability of a molecule having an Mr of 72 is not 0.1875

Explain how displacement reactions involving halogens and halides provide evidence for the trend in reactivity in Group 7 of the Periodic Table. Include examples of reactions in your answer.

Paint can be used to coat iron, which protects iron from rusting.

Give the chemical name for rust.

Explain how painting prevents iron from rusting.

Steel is made from iron and carbon. Explain how the difference in malleability of pure iron and high-carbon steel affects the uses of these materials.

Zinc reacts with dilute sulfuric acid to produce zinc sulfate and hydrogen. This is the equation for the reaction. Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g) A mass of 16 g of zinc reacts with an excess of sulfuric acid. Calculate the maximum volume, at rtp, of hydrogen produced. [for hydrogen at rtp, molar volume = 24 dm³] volume of hydrogen = dm³

A solution of zinc sulfate is electrolysed to form zinc on the negative electrode.

The ionic half-equation at the negative electrode is Zn²⁺ + 2e– → Zn Give a reason why this half-equation shows reduction.

Complete the ionic half-equation for the reaction that could occur at the positive electrode. ……… …… OH– → … … … … … O₂ + … … … … … H₂O + … … … … … e–

A sample of the solution surrounding the positive electrode is tested with universal indicator. Explain the final colour of the universal indicator.

Steam can be used to manufacture ethanol.

Give the other reactant needed for this reaction.

State the pressure and catalyst used for this reaction to manufacture ethanol. pressure catalyst

The glucose in grapes can be fermented to make ethanol.

State the condition needed to prevent the formation of ethanoic acid.

Explain why fermentation needs to happen in the range of 30 °C to 40 °C.

Grapes also contain esters. This is the structural formula of an ester. CH₃COOCH₂CH₂CH₂CH₃

Draw the displayed formula of this ester.

Deduce the name of the carboxylic acid and the name of the alcohol that react to form this ester. carboxylic acid alcohol

These are the structural formulae of two monomers that are used to make a polyester. O O HO C CH₂CH₂ C OH HO CH₂CH₂CH₂ OH

Give the name of this type of polymerisation.

Draw the structure of the repeat unit of the polyester formed from the two monomers.

Identify the small molecule formed when these two monomers react together.

A student uses this apparatus to investigate the decomposition of hydrogen peroxide solution. hydrogen peroxide solution 0 20 40 60 80 100 manganese(IV) oxide This is the equation for the reaction. 2H₂O₂ → 2H₂O + O₂

Give a chemical test for the presence of water.

In the first experiment the student uses hydrogen peroxide solution with a concentration of 0.020 mol / dm³. The graph shows the student’s results. Volume of oxygen 50 in cm³ 0 30 60 90 120 150 180 210 240 270 300 Time in seconds In a second experiment, the student uses hydrogen peroxide solution with a concentration of 0.025 mol / dm³. All other conditions remain the same.

On the grid, draw the curve you would expect the student to obtain from the second experiment.

On the grid, draw the curve you would expect the student to obtain for the second experiment carried out at a lower temperature.

Potassium iodide has been suggested as an alternative catalyst to manganese(IV) oxide. Describe a method to show which catalyst is more effective for the decomposition of hydrogen peroxide.

The equation shows one of the possible substitution reactions that occurs during the reaction between methane and chlorine. CH₃Cl + 3Cl₂ → CCl₄ + 3HCl ΔH = –339 kJ / mol

Complete the reaction profile diagram to show the levels of the reactants, the products and the activation energy, Ea . energy

The table gives some bond energies. Bond C H Cl Cl H Cl Bond energy in kJ / mol 414 242 431 Using information from the equation and the table, calculate the bond energy of the C Cl bond. C Cl bond energy = kJ / mol