4CH1/1C — January 2022 (Edexcel IGCSE Chemistry): Past Paper

This question is about mixtures and compounds.

The box gives some methods used to separate mixtures. chromatography crystallisation fractional distillation simple distillation Choose methods from the box to answer the following questions. Each method may be used once, more than once or not at all.

Identify a method to separate a single food dye from a mixture of food dyes.

Identify a method to separate gasoline from crude oil.

Identify a method to separate water from copper(II) sulfate solution.

The diagram represents a molecule. Explain why this molecule is a compound.

The molecular formula of another compound is C₃H₅N₃O₉

State the number of different elements in C₃H₅N₃O₉

Determine the number of atoms in a molecule of C₃H₅N₃O₉

This question is about rusting.

A simplified formula for rust is Fe₂O₃

Name the two substances needed for iron to rust. 1 2

Give the chemical name for rust.

What type of reaction occurs in the rusting of iron?

Some iron objects are coated with a layer of zinc to prevent rusting.

Name this type of rust prevention.

Explain how this type of rust prevention continues to protect iron when the layer of zinc is damaged.

Give two other methods used to prevent iron from rusting. 1 2

This question is about states of matter.

The box gives words relating to changes of state. condensation cooling evaporation freezing melting sublimation Complete the table by giving the correct word from the box for each change of state. Change of state Name of change solid to liquid solid to gas liquid to solid

When ammonia gas and hydrogen chloride gas mix, they react together to form a white solid called ammonium chloride. The equation for the reaction is NH₃(g) + HCl(g) → NH₄Cl(s) A teacher soaks a piece of cotton wool in concentrated ammonia solution and another piece of cotton wool in concentrated hydrochloric acid. The teacher places the two pieces of cotton wool at opposite ends of a glass tube at the same time. After several minutes, a white ring of solid ammonium chloride forms. cotton wool soaked cotton wool soaked white ring of in concentrated in concentrated ammonium chloride ammonia solution hydrochloric acid

State the name given to the spreading out of gas particles.

State how the diagram shows that the particles of ammonia gas are travelling at higher speeds than the particles of hydrogen chloride gas.

Gas particles travel at high speeds. Give a reason why the white ring of ammonium chloride takes several minutes to form.

Concentrated ammonia solution and concentrated hydrochloric acid are corrosive. Give one safety precaution the teacher should take.

A teacher uses this apparatus to find the percentage of oxygen in a gaseous mixture of oxygen and argon. mixture of oxygen and argon glass tube copper powder syringe A syringe B heat This is the teacher’s method. Step 1 heat the copper powder Step 2 push the plunger on syringe A to pass the mixture of oxygen and argon over the hot copper so that the mixture moves into syringe B Step 3 push the plunger on syringe B to pass the mixture of oxygen and argon over the hot copper so that the mixture moves into syringe A Step 4 record the reading on syringe A Step 5 repeat Steps 2, 3 and 4 a number of times The volume of gas decreases as the oxygen reacts with the copper. Argon is unreactive so does not react with the copper. The copper powder turns black.

Give a reason why the copper powder is heated.

State why argon is unreactive.

Give the name of the black powder that forms when the oxygen reacts with the copper.

The table shows the teacher’s results

State how the results show that all the oxygen has reacted.

The volume of gas in the glass tube and connecting tubes is 175 cm³. Use this value and the results table to calculate the percentage of oxygen in the mixture of oxygen and argon. percentage of oxygen = %

Suggest one reason why the calculated percentage of oxygen in the mixture may not be accurate.

Complete the table to show the relative mass and relative charge of a proton and a neutron. Proton Electron Neutron Relative mass 1/2000 Relative charge −1

Magnesium has three isotopes.

State the meaning of the term isotopes.

The symbol for an atom of one isotope of magnesium is 12 Mg Give the number of protons, neutrons and electrons in one atom of this isotope. number of protons number of neutrons number of electrons

A sample of magnesium contains these percentages of the three isotopes. Mg‑24 = 79.00 % Mg‑25 = 10.00 % Mg‑26 = 11.00 % Use this information to show that the relative atomic mass of magnesium is 24.32

One mole of magnesium has a mass of 24.32 g. There are 6.022 × 10²³ atoms in one mole. Calculate the mass, in grams, of one atom of magnesium. Give your answer to 4 significant figures. mass = g

The equation for the reaction between magnesium and oxygen is 2Mg + O₂ → 2MgO Determine the maximum amount, in moles, of magnesium oxide that can be produced from 0.50 mol of magnesium and 0.20 mol of oxygen. amount = mol

This question is about sodium oxide, Na₂O

The diagram shows the electronic configuration of atoms of sodium and oxygen. Sodium Oxygen Describe the changes in the electronic configuration of the atoms of sodium and oxygen to form the ions in sodium oxide.

Calculate the relative formula mass (Mr ) of sodium oxide, Na₂O, using information from the Periodic Table. Mr =

Explain why solid sodium oxide does not conduct electricity.

Give a test to show that sodium oxide contains sodium ions.

When sodium oxide is heated it reacts to form sodium metal and sodium peroxide, Na₂O₂ Complete the equation for this reaction. Na₂O →

This question is about soluble and insoluble compounds. A precipitate is an insoluble compound formed when solutions of soluble compounds react after mixing.

Different solutions are mixed in separate test tubes. Tube 1 copper(II) sulfate solution and calcium chloride solution Tube 2 magnesium nitrate solution and potassium sulfate solution Tube 3 sodium carbonate solution and copper(II) sulfate solution In which of the tubes will a precipitate form?

A student mixes solutions, containing equal amounts in moles, of silver nitrate and sodium chloride. The equation for the reaction between silver nitrate solution and sodium chloride solution is AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq)

State the colour of the precipitate of silver chloride.

The student wants to obtain pure, dry crystals of sodium nitrate. Crystals of sodium nitrate decompose at temperatures above 300 °C. Describe a method the student could use to obtain pure, dry crystals of sodium nitrate.

Give an advantage of mixing solutions containing equal amounts, in moles, of silver nitrate and sodium chloride.

The table shows the structures of six organic compounds

Give the letter of a compound not shown as a displayed formula.

Give the letter of a saturated compound with the general formula CnH2n

Name compound E.

Explain why compound A and compound D are isomers.

Compound F reacts with bromine in the presence of ultraviolet radiation.

Complete the equation for the reaction. CH₄ + Br₂ →

Give the name of this type of reaction.

Another compound, G, has this percentage composition by mass. C = 37.8 % H = 6.3 % Cl = 55.9 % Show by calculation that the empirical formula of compound G is C₂H₄Cl

The relative formula mass (Mr ) of G is 127 Determine the molecular formula of G. molecular formula =

Compound E is used to make an addition polymer.

Complete the equation to show part of the polymer formed from two molecules of compound E.

Give one problem caused by the disposal of addition polymers.

A student uses this apparatus to investigate the rate of reaction between calcium carbonate chips and dilute hydrochloric acid. cotton wool plug calcium carbonate dilute hydrochloric acid chips balance 124.05 g Every 20 seconds the student records the reading on the balance.

Explain why using a cotton wool plug increases the accuracy of the student’s results.

Complete the equation for the reaction by adding the state symbols. CaCO₃( ) + 2HCl( ) → CaCl₂(aq) + H₂O( ) + CO₂( )

The student uses the balance readings to find the decrease in mass of the flask and contents. The graph shows the student’s results

Give a reason why there are some calcium carbonate chips remaining in the flask when the reaction stops.

State how the student would know when the reaction has stopped.

Use the graph to determine the amount, in moles, of carbon dioxide produced during the reaction. [Mr of CO₂ = 44] amount = mol

Use the graph to calculate the rate of reaction, in grams per second, at time 60 seconds. Show your working on the graph. rate of reaction = g / s

The student repeats the investigation by diluting the original hydrochloric acid. The student then determines the initial rate of reaction at different percentage concentrations of the original hydrochloric acid. The graph shows the student’s results. 0.025 0.020 Initial rate of reaction 0.015 in g / s 0.010 0.005 0 20 40 60 80 100 Percentage concentration of original hydrochloric acid

Describe the relationship between the initial rate of reaction and percentage concentration of the original hydrochloric acid.

Explain why changing the concentration of hydrochloric acid has an effect on the initial rate of reaction.

This question is about substances with covalent bonds.

Draw a dot and cross diagram to show the outer shell electrons in a molecule of nitrogen, N₂

Describe the forces of attraction in a covalent bond.

The diagram shows three different structures of carbon. Structure A Graphite C₆₀ fullerene

Name structure A.

Graphite and C₆₀ fullerene contain covalent bonds, but have different structures. Explain why C₆₀ fullerene has a much lower melting point than graphite. Refer to structure and bonding in your answer.

A student uses this apparatus to heat crystals of hydrated zinc sulfate and collect the liquid produced.

Describe a chemical test to show that the colourless liquid contains water.

Describe a physical test to show the colourless liquid is pure water.

The equation for the decomposition of hydrated zinc sulfate is ZnSO₄·7H₂O(s) → ZnSO₄(s) + 7H₂O(l) The student records these masses. mass of boiling tube = 41.64 g mass of boiling tube + ZnSO₄·7H₂O = 54.46 g Calculate the maximum volume, in cm³, of pure water that could be produced. Give your answer to 1 decimal place. [1.00 cm³ of pure water has a mass of 1.00 g] [Mr of ZnSO₄·7H₂O = 287 Mr of H₂O = 18] maximum volume of pure water = cm³

In an experiment using a different mass of ZnSO₄·7H₂O the maximum volume of pure water that could be produced is 8.5 cm³. The student collected the pure water and calculated the percentage yield to be 20.3 %.

Calculate the volume, in cm³, of pure water collected. volume of pure water = cm³

Explain an improvement to the apparatus that would increase the percentage yield of pure water.