4CH1/1CR — June 2019 (Edexcel IGCSE Chemistry): Past Paper

This question is about the three states of matter, solid, liquid and gas.

Solids, liquids and gases can be changed from one state to another. The box gives the names of some changes of state. condensing evaporation melting sublimation Use words from the box to complete the sentences. Each word may be used once, more than once or not at all.

The change from solid to liquid is called

The change from liquid to gas is called

The change from solid to gas is called

Describe the arrangement and the movement of particles in a solid.

This question is about some elements in Group 1 of the Periodic Table.

The table gives some statements about the reaction of potassium with water. Place ticks (✓) in three boxes to show which three statements are correct. Statement potassium reacts more vigorously than sodium when added to water potassium sinks to the bottom of the water bubbles of oxygen gas are produced a lilac flame is seen potassium moves around a solution of potassium oxide is formed

After the reaction of potassium with water is complete, a few drops of universal indicator are added to the solution formed. The universal indicator turns purple.

Suggest a value for the pH of the solution.

Give the formula of the ion responsible for this pH value.

Sodium burns in oxygen to produce sodium oxide. Complete the equation for this reaction Na + O₂ → Na₂O

A student uses paper chromatography to investigate the dyes in five different inks, V, W, X, Y and Z. This is what she uses.

• a beaker
• a piece of chromatography paper with a pencil line drawn near the bottom of the paper
• a solvent
• inks V, W, X, Y and Z

Describe how the student should set up and carry out her experiment. You may draw a diagram to help with your answer.

Explain why the line on the paper is drawn in pencil rather than in ink.

The chromatogram shows the results for inks V, W, X, Y and Z

Explain which ink contains a dye that is insoluble in the solvent.

Explain which two inks contain the dye that is likely to be the most soluble in the solvent.

Explain which two inks may contain only one dye.

One dye in ink Y moves 4.3 cm when the solvent front moves 6.5 cm. Calculate the Rf value for this dye. Give your answer to 2 significant figures. Rf value =

This question is about hydrocarbons.

State the meaning of the term hydrocarbon.

One homologous series of hydrocarbons is the alkanes. Pentane (C₅H₁₂) is an alkane.

When pentane burns completely in oxygen, carbon dioxide and water are produced. Give a chemical equation for this combustion reaction.

Incomplete combustion can occur when the oxygen supply is limited. Give the names of two products of the incomplete combustion of pentane. 1 2

One of the products of incomplete combustion is a poisonous gas. State why this gas is poisonous to humans.

C₅H₁₂ has three isomers. The displayed formula for one of these isomers is Draw the displayed formulae of the other two isomers.

Another homologous series of hydrocarbons is the alkenes. Alkenes are unsaturated hydrocarbons.

Give the general formula for the alkenes.

State the meaning of the term unsaturated.

Describe a test to show that a hydrocarbon is unsaturated.

A student uses this apparatus to investigate the rate of reaction between marble chips and dilute hydrochloric acid. cotton wool dilute hydrochloric acid marble chips balance

During the reaction, the reading on the balance decreases because mass is lost from the flask.

Explain how using the cotton wool increases the accuracy of this investigation.

Why is mass lost from the flask?

This is the equation for the reaction between marble chips and dilute hydrochloric acid. Complete the equation by adding the state symbols. CaCO₃ ( ) + 2HCl ( ) → CaCl₂ ( ) + H₂O ( ) + CO₂ ( )

The student uses large marble chips in the investigation. This is a graph of his results. Mass loss Time The student repeats the experiment using the same total mass of smaller marble chips. On the graph, draw the curve that would be obtained. [assume the marble chips are in excess]

The rate of this reaction can be altered by increasing the temperature or by increasing the concentration of the hydrochloric acid.

Explain, using the particle collision theory, how increasing the concentration of the hydrochloric acid would affect the rate of this reaction.

Explain, using the particle collision theory, how increasing the temperature would affect the rate of this reaction.

Poly(chloroethene) is a polymer. It is made from its monomer, chloroethene.

Chloroethene has the percentage composition by mass C = 38.4% H = 4.8% Cl = 56.8% Show, by calculation, that the empirical formula of chloroethene is C₂H₃Cl

The molecular formula of chloroethene is also C₂H₃Cl Chloroethene can be prepared by a two‑stage process. In stage 1, ethene reacts with chlorine in the presence of an iron(III) chloride catalyst to form dichloroethane. The reaction is exothermic. C₂H₄ + Cl₂ → C₂H₄Cl₂

Give the formula of iron(III) chloride.

State the purpose of using a catalyst.

State the meaning of the term exothermic.

What type of reaction occurs in stage 1 between ethene and chlorine?

In stage 2, dichloroethane decomposes into chloroethene and hydrogen chloride. Give a chemical equation for this reaction.

Draw the displayed formula of • chloroethene • the repeat unit of poly(chloroethene) chloroethene repeat unit of poly(chloroethene)

Draw a dot‑and‑cross diagram to represent a molecule of chloroethene. Show only the outer electrons of each atom.

No printed figure accompanies this part — in the paper you would draw the diagram (or label the apparatus) in the answer space provided.

A student makes some magnesium nitrate crystals from magnesium oxide and dilute nitric acid. The equation for the reaction is MgO(s) + 2HNO₃(aq) → Mg(NO₃)₂(aq) + H₂O(l)

Give the formula of each ion in magnesium nitrate and

A student has a beaker containing dilute nitric acid. Describe a method that she could use to prepare a pure, dry sample of magnesium nitrate crystals from magnesium oxide.

Magnesium nitrate crystals contain water of crystallisation with the formula Mg(NO₃)₂.6H₂O

Show by calculation that the relative formula mass of Mg(NO₃)₂.6H₂O is 256.

Show that the maximum mass of Mg(NO₃)₂.6H₂O that could be made from 0.050 mol of nitric acid is about 6 g.

The actual mass of crystals that the student obtains is 4.8 g. Calculate the percentage yield of Mg(NO₃)₂.6H₂O in this experiment. percentage yield = %

A student investigates the neutralisation reaction between sodium hydroxide and nitric acid. This is her method.

• pour 20 cm³ of sodium hydroxide solution into a polystyrene cup
• record the temperature of the sodium hydroxide solution
• add 5 cm³ of dilute nitric acid to the cup
• stir the mixture and record the highest temperature reached
• add further 5 cm³ portions of dilute nitric acid, recording the highest temperature reached each time, until a total of 40 cm³ of acid has been added

Give a word equation for this neutralisation reaction.

Explain why a polystyrene cup is used rather than a beaker.

Give a safety precaution that the student should take when using sodium hydroxide solution.

The table shows the student’s results

Plot the results on the grid. Draw a straight line of best fit through the first five points and another straight line of best fit through the last four points. Make sure that the two lines cross

The point where the lines cross shows • the volume of acid needed to exactly neutralise the alkali • the maximum temperature reached Use your graph to determine these values. volume of acid = cm³ maximum temperature = °C

Diamond is a naturally‑occurring form of carbon. It has a giant molecular structure. Explain, with reference to its structure and bonding, why diamond has a high melting point.

C₆₀ fullerene is another form of carbon. The diagram shows a molecule of C₆₀ fullerene.

Explain why C₆₀ fullerene has a much lower melting point than diamond.

C₆₀ fullerene is used by doctors when injecting medicines into their patients. C₆₀ fullerene allows medicines, which might damage some parts of the body, to reach the part of the body where they are needed. Suggest why C₆₀ fullerene is suitable for this purpose.

Graphite is another naturally‑occurring form of carbon. Graphite can be used in pencils because it is soft and can leave marks on paper. Graphite can also be used as a conductor of electricity. Explain why graphite is soft and conducts electricity. Refer to structure and bonding in your answer.

A student investigates the reaction between zinc and copper(II) sulfate solution. The equation for the reaction is Zn + CuSO₄ → Cu + ZnSO₄ This is his method.

• add exactly 25.0 cm³ of copper(II) sulfate solution to a polystyrene cup
• record the temperature of the solution
• add about 5 g of zinc powder (an excess) and stir the mixture
• record the highest temperature reached

Suggest why it is not important to add an exact mass of zinc powder.

State the colour change of the solution. from to

The table shows the student’s results

Show that the heat energy change (Q) is about 1300 J. [for the solution, c = 4.18 J/g/°C] [mass of 1.00 cm³ of solution = 1.00 g]

The mass of anhydrous copper(II) sulfate (CuSO₄) used to make 25.0 cm³ of solution is 2.00 g. Calculate the amount, in moles, of CuSO₄ in 2.00 g. [Mr of CuSO₄ = 159.5] amount of CuSO₄ = mol

Calculate the value of the enthalpy change (ΔH), in kilojoules per mole, for the reaction between zinc and copper(II) sulfate. Include a sign in your answer. ΔH = kJ/mol