4CH1/1CR — January 2020 (Edexcel IGCSE Chemistry): Past Paper

The diagram shows the particles in the atom of an element

Particle Y is a proton. What is particle Z?

Which of these has the smallest mass?

What is the mass number of this atom?

What is the atomic number of this atom?

Identify the element that contains this atom.

State what is formed when this atom loses its outer shell electrons.

This question is about states of matter.

The diagram shows how the particles of a substance are arranged in two different states. solid liquid gas

Complete the diagram to show how particles are arranged in the liquid state.

Identify the state of matter in which the particles have the most energy.

The state symbols (s), (l), (g) and (aq) are often used in chemistry. The table shows some physical changes. Complete the table by giving the state symbol before and after each change. State symbol Physical change before change after change water evaporates crystals of iodine sublime ice melts

Explain why hot water evaporates more quickly than cold water.

The Group 7 elements are called halogens. Halogens form compounds called halides. Three of the halogens are represented by the formulae X₂ , Y₂ and Z₂ Solutions of these halogens are added separately to solutions of sodium halides, NaX, NaY and NaZ. The table shows whether or not a reaction occurs

Use the information in the table to deduce the order of reactivity of the halogens X₂ , Y₂ and Z₂ most reactive least reactive

An aqueous solution of halogen Y₂ is orange. This solution is decolourised when it reacts with an alkene. Deduce the identity of halogen Y₂

The table shows some physical properties of the halogens. Complete the table by predicting a boiling point for chlorine, the state of fluorine at room temperature and the colour of astatine. State at Halogen Boiling point in °C Colour room temperature fluorine −188 yellow chlorine gas green bromine 59 liquid red-brown iodine sublimes solid grey astatine 337 solid

Why do the halogens have similar chemical properties?

A teacher uses this apparatus to demonstrate the reaction between chlorine gas and iron wool. The teacher does the reaction in a fume cupboard. iron wool unreacted chlorine chlorine heat

Suggest why the teacher does the reaction in a fume cupboard.

The product of the reaction between iron and chlorine is iron(III) chloride. The ions in iron(III) chloride are Fe³⁺ and Cl− Use this information to give the chemical equation for this reaction.

This question is about ammonium chloride.

Give the formula of the ammonium ion.

Describe a test to show that ammonium chloride contains ammonium ions.

The equation shows the thermal decomposition of ammonium chloride. NH₄Cl(s) U NH₃(g) + HCl(g) State what the U symbol indicates about this reaction.

The diagram shows the formation of ammonium chloride in a glass tube. cotton wool soaked in cotton wool soaked in concentrated hydrochloric acid ammonium chloride concentrated ammonia solution

Explain how the mean speed of ammonia molecules compares with the mean speed of hydrogen chloride molecules.

Gas particles travel very quickly. Give two reasons why it takes several minutes for the ammonium chloride to form. 1 2

A teacher uses the reaction between phosphorus and oxygen to calculate the percentage of oxygen in air.

She uses this apparatus and excess phosphorus.

Apparatus (printed in the paper): piece of phosphorus on a wire — scale in 0.5 cm3 divisions — glass tube full of air — water.

The volume of gas in the tube decreases as the phosphorus reacts with oxygen. The teacher measures the volume of gas in the tube at one-minute intervals. The table shows the teacher's results.

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

Give one change to this experiment that would make the results more accurate.

Use the results to calculate the percentage of oxygen in air. Give your answer to one decimal place. percentage = %

The reaction between magnesium and copper(II) sulfate solution is exothermic. This apparatus is used to measure the temperature increase when excess magnesium is added to 100 cm³ of copper(II) sulfate solution

State why a reaction occurs when magnesium is added to copper(II) sulfate solution.

Complete the word equation for this reaction. magnesium + copper(II) sulfate o +

The temperature at the start of the reaction is 20.2 °C. The maximum temperature recorded is 56.3 °C.

Calculate the heat energy change, in joules, for the reaction. [mass of 1.00 cm³ of solution = 1.00 g] [c for the solution = 4.2 J/g/ °C] heat energy change = J

Explain why it is better to use a polystyrene cup rather than a glass beaker in this experiment.

The reaction between zinc and copper(II) sulfate solution is also exothermic.

A mass of 0.500 g of zinc is reacted with an excess of copper(II) sulfate solution. The heat energy change is 1.67 kJ. Calculate the molar enthalpy change, ΔH, in kJ/mol. Include a sign in your answer. Give your answer to three significant figures. ΔH = kJ/mol

The ionic equation for the reaction between zinc and copper(II) sulfate is Zn(s) + Cu²⁺(aq) o Zn²⁺(aq) + Cu(s) Explain why this is a redox reaction.

A student investigates the reaction between sodium hydroxide solution and hydrochloric acid. He uses this method. Step 1 add 50 cm³ of dilute hydrochloric acid to a conical flask Step 2 add a 5 cm³ portion of sodium hydroxide solution to the conical flask Step 3 test the pH of the mixture using both universal indicator paper and a pH meter The student repeats step 2 and step 3 until a total of 50 cm³ of sodium hydroxide solution has been added.

State the piece of apparatus that should be used to measure 50 cm³ of hydrochloric acid.

Name the type of reaction that occurs between hydrochloric acid and sodium hydroxide.

Graph 1 shows how the pH of the mixture changes as the sodium hydroxide solution is added. pH 0 10 20 30 40 50 Volume of sodium hydroxide solution in cm³ Graph 1

Determine the pH after 40 cm³ of sodium hydroxide solution has been added.

Suggest the colour of the universal indicator paper when these volumes of sodium hydroxide solution have been added. 15 cm³ 30 cm³

Give the formula of the ion that causes sodium hydroxide to be alkaline.

Another student investigates how the temperature changes when the sodium hydroxide solution is added to the hydrochloric acid. The hydrochloric acid and the sodium hydroxide solution are at the same temperature at the start of the investigation. The student records the temperature of the mixture after adding each 5 cm³ portion of sodium hydroxide solution. Graph 2 shows her results. Temperature in °C 0 5 10 15 20 25 30 35 40 45 50 Volume of sodium hydroxide solution in cm³ Graph 2 Explain the shape of graph 2.

The diagram shows the arrangement of electrons in an atom of calcium and in an atom of chlorine. Ca Cl Describe, in terms of electrons, what happens when calcium reacts with chlorine to form the ionic compound calcium chloride, CaCl₂

Describe tests to show that an aqueous solution of calcium chloride contains calcium ions and chloride ions. calcium ions chloride ions

Solid calcium chloride does not conduct electricity. Aqueous solutions of calcium chloride do conduct electricity. A student uses this method to investigate how the conductivity of a solution changes when calcium chloride is dissolved in pure water. Step 1 add 100 cm³ of pure water to a beaker Step 2 add one spatula of solid calcium chloride to the beaker Step 3 stir the solution Step 4 measure the conductivity of the solution Step 5 repeat until nine spatulas of solid calcium chloride have been added The table shows the student’s results. Number of spatulas Conductivity of solution of calcium chloride in arbitrary units 0 0 1 6 2 12 3 12 4 24 5 30 6 36 7 36 8 36 9 36

Plot the results on the grid and draw two straight lines of best fit. Ignore the anomalous result. Conductivity of solution 20 in arbitrary units 0 1 2 3 4 5 6 7 8 9 Number of spatulas of calcium chloride

State the trend shown on the graph for the first six spatulas of calcium chloride.

Suggest an error the student could have made to cause the anomalous result.

Describe another way to make solid calcium chloride conduct electricity.

This question is about alkenes and polymers.

Ethene (C₂H₄) can be represented by different types of formula. Complete the table by giving the missing information. Molecular formula C 2 H4 Empirical formula General formula

Ethene is a member of the homologous series of alkenes. All members of the same homologous series have the same general formula. Give two other characteristics of a homologous series. 1 2

Ethene is used to make poly(ethene).

State the type of polymerisation used to form poly(ethene).

Complete the equation for the polymerisation of ethene.

Poly(ethene) is used to make plastic bags. Corn starch from plants can also be used to make polymers for plastic bags. The table gives some information about poly(ethene) and polymers made from corn starch. Poly(ethene) Polymers from corn starch Cost per tonne £1500 £3700 Relative strength 100 50 Time to decompose estimated 450 years 3–6 months Use the information in the table and your knowledge to discuss the advantages and disadvantages of using poly(ethene) to make plastic bags.

The diagram shows the repeat unit of another polymer. H H C H H C C H H Draw the displayed formula of the monomer used to make this polymer.

This question is about carbon and its compounds.

Draw a dot-and-cross diagram to show the outer shell electrons in a molecule of carbon dioxide, CO₂

The atoms in carbon dioxide are held together by covalent bonds. Describe the forces of attraction in a covalent bond.

The diagram shows three different structures of carbon. diamond graphite C₆₀ fullerene

Explain why graphite conducts electricity.

Explain why diamond has a much higher melting point than C₆₀ fullerene. Refer to structure and bonding in your answer.

This question is about the reduction of metal oxides.

Solid oxides of copper can be reduced by reacting them with methane gas. Complete the equation for the reaction between copper(II) oxide and methane. Include state symbols CuO( ) + CH₄( ) o Cu( ) + CO₂( ) + H₂O( )

A teacher uses this apparatus to demonstrate the reaction between a different oxide of copper and methane. excess methane burning methane gas oxide of copper heat in weighing boat

The teacher heats the oxide of copper until the reaction is complete. The table shows the teacher’s results. Mass in g empty weighing boat 15.05 weighing boat + oxide of copper 18.63 weighing boat + copper 18.23 Use the teacher’s results to show that the empirical formula of this oxide of copper is Cu₂O

The teacher wears safety glasses and a lab coat during the demonstration. Give one other safety precaution that she should take.

Iron forms when iron(III) oxide is heated with carbon. The equation for the reaction is Fe₂O₃ + 3C o 2Fe + 3CO

State how the equation shows that iron(III) oxide is reduced.

State why carbon monoxide should not be released into the atmosphere.

Calculate the maximum mass, in tonnes, of iron that can be produced when 30.0 tonnes of iron(III) oxide are reacted with an excess of carbon. [1 tonne = 1.0 × 10⁶ g] mass = tonnes

A mixture of 25 000 mol of iron(III) oxide and 840 000 g of carbon is heated. Use this equation to show that the iron(III) oxide is in excess. Fe₂O₃ + 3C o 2Fe + 3CO