4CH1/1C — November 2020 (Edexcel IGCSE Chemistry): Past Paper

This question is about chemical elements. Use the Periodic Table to help you answer this question.

Identify the element with atomic number 5

Give the symbol of a metallic element in Period 3

Identify the element whose atoms contain 14 protons.

Identify the element whose atoms have the electronic configuration 2.5

Give the name of the compound formed between oxygen and the element with atomic number 13

The position of an element in the Periodic Table can be used to predict its properties.

Which group contains elements that are all unreactive?

Which of these is the least reactive element in Group 1?

The boxes list changes that may happen in a laboratory and the names of some changes. Draw one straight line from each change to its correct name. Change Name of change diffusion dissolving ice turns into water evaporation solid carbon dioxide turns directly into a gas freezing a solute is stirred into a solvent melting sublimation

A student has two solids, X and Y. One of these solids is a pure substance and the other is a mixture. Describe how the student could identify which solid is pure and which is a mixture by measuring a physical property of each solid.

This question is about metals.

Metals can be arranged in a reactivity series based on their reactions with water and their reactions with dilute hydrochloric acid. The table shows how four metals, P, Q, R and S, react with water and with dilute hydrochloric acid. Reaction with Reaction with Metal water dilute hydrochloric acid P no reaction hydrogen gas forms very slowly Q no reaction no reaction R hydrogen gas forms very quickly not done S hydrogen gas forms quickly hydrogen gas forms very quickly

Identify which of the metals P, Q, R or S could be gold.

Suggest why the reaction between metal R and dilute hydrochloric acid was not done.

Use the information in the table to place the metals in order of reactivity from most reactive to least reactive. most reactive least reactive

Zinc is used to coat iron gates to prevent the iron from rusting.

State the name of this method of preventing iron from rusting.

State another method of preventing iron from rusting.

A mixture of zinc powder and copper(II) oxide is heated. The chemical equation for the reaction that takes place is Zn + CuO → ZnO + Cu

State how the reaction shows that zinc is more reactive than copper.

Explain which substance is the oxidising agent.

Sodium hydroxide dissolves in water, forming a strongly alkaline solution. Ammonia dissolves in water, forming a slightly less alkaline solution.

Identify the ion that makes the sodium hydroxide solution alkaline.

What is a possible pH of ammonia solution?

When ammonia solution reacts with sulfuric acid, a neutralisation reaction occurs and ammonium sulfate forms.

How does the sulfuric acid act in this reaction?

The diagram shows a beaker containing some ammonia solution and a few drops of phenolphthalein indicator. ammonia solution and phenolphthalein indicator Dilute sulfuric acid is added to the beaker until it is in excess. What are the colours of the phenolphthalein indicator before and after adding excess sulfuric acid? Before After

Ammonium sulfate is used by gardeners as a fertiliser because it contains nitrogen.

Explain why the chemical formula of ammonium sulfate is (NH₄)₂SO₄ Refer to the charges on the ions in your answer.

Calculate the relative formula mass of ammonium sulfate, (NH₄)₂SO₄ relative formula mass =

Calculate the mass, in grams, of nitrogen in 1.0 kg of ammonium sulfate. mass = g

Chlorine, bromine and iodine are elements in the Periodic Table. Explain how the position of these elements in the Periodic Table depends on their electronic configurations.

Chlorine reacts with methane to form CH₃Cl and HCl

State the condition necessary for this reaction.

Give the equation for this reaction.

The bonds in a molecule of CH₃Cl are covalent. Explain, in terms of electrostatic attractions, what is meant by a covalent bond.

Draw a dot‑and‑cross diagram for a molecule of CH₃Cl Show only the outer electrons of the atoms. H H C Cl H

CH₃Cl has a simple molecular structure. Explain why CH₃Cl has a low boiling point.

Graphite is another substance that contains covalent bonds. The diagram shows the structure of graphite. Most covalent substances do not conduct electricity. Explain why graphite is able to conduct electricity.

The table shows the molecular formulae of six organic compounds, A, B, C, D, E and F. A B C D E F C₂H₄ C₂H₆ C₃H₆ C₃H₈ C₄H₈ C₄H₁₀

Explain which homologous series compound B belongs to.

Give the letter of the compound that has the same empirical formula as its molecular formula.

Compound F exists as two isomers. Explain what is meant by the term isomers. Include the structures of the two isomers of compound F in your answer.

Describe how compound D can be obtained from crude oil using the industrial process of fractional distillation.

Compound C can be used to make a polymer.

State the type of polymer formed from compound C.

Name the polymer formed from compound C.

Draw the structure of this polymer. Include the displayed formula of the repeat unit.

Dilute hydrochloric acid reacts with a solution of sodium thiosulfate (Na₂S₂O₃) to form a precipitate. The equation for the reaction is Na₂S₂O₃(aq) + 2HCl(aq) → 2NaCl(aq) + S(s) + H₂O(l) + SO₂(g)

State the name of the precipitate that forms.

The reaction is often used to investigate rates of reaction. The diagram shows the apparatus a student uses to investigate the effect of temperature on the rate of the reaction. eye conical flask sodium thiosulfate solution paper with cross drawn on it This is the student’s method. ● pour 50 cm³ of cold sodium thiosulfate solution into a conical flask and heat it to 20 °C ● draw a cross (X) on a piece of paper and place it under the flask ● add 5 cm³ of dilute hydrochloric acid to the flask ● look at the cross from above and record the time taken until the cross cannot be seen The student repeats the experiment four times, using sodium thiosulfate solution at a different temperature each time. He keeps the volumes of sodium thiosulfate solution and hydrochloric acid constant in each experiment. Give two other factors that the student should keep constant. 1 2

The table shows the student’s results. Temperature Time until cross in °C cannot be seen in s 20 400 30 188 40 84 50 44 60 24 The highest temperature the student uses is 60 °C because he thinks the results might not be as accurate at temperatures higher than 60 °C. Suggest a reason why the results might not be as accurate at temperatures higher than 60 °C.

The student wants to compare the rates of the reaction at the different temperatures. He uses this formula to obtain a value for each rate of reaction rate = time in s The table shows the value of the rate of reaction at each temperature. Temperature Time until cross Rate of reaction in °C cannot be seen in s in s–1 20 400 0.0025 30 188 0.0053 40 84 0.012 50 44 0.023 60 24 0.042 Plot the values of temperature and rate of reaction on the grid. Draw a curve of best fit through the points. 0.05 0.04 0.03 Rate of reaction in s–1 0.02 0.01 0 10 20 30 40 50 60 70 Temperature in °C

Use the graph to determine a value for the rate of the reaction at 45 °C. Show on the graph how you obtained your answer. rate of reaction = s−1

Calculate the time that it would take for the cross not to be seen at 45 °C. time = s

Describe the relationship between rate of reaction and temperature shown by the graph.

Explain, in terms of particle collision theory, the effect that increasing the temperature has on the rate of a reaction.

A student uses this apparatus to investigate the heat energy change when a salt dissolves in water to form a solution. polystyrene cup distilled water This is the student’s method.

• add 50 cm³ of distilled water to a polystyrene cup
• record the initial temperature of the water
• add a known mass of solid anhydrous copper(II) sulfate to the polystyrene cup and stir the solution with the thermometer until all the solid has dissolved
• record the maximum temperature of the copper(II) sulfate solution

Name the piece of apparatus the student should use to add the distilled water to the polystyrene cup.

The student stirs the solution to help the solid dissolve more quickly. Suggest another reason why the student stirs the solution.

State the colour of the copper(II) sulfate solution.

The diagram shows the temperatures in one experiment. °C 25 °C 30 20 25 initial temperature maximum temperature Complete the table, giving all values to the nearest 0.1 °C. maximum temperature in °C initial temperature in °C increase in temperature in °C

In a second experiment, when a student dissolves the anhydrous copper(II) sulfate in 50 cm³ of distilled water, the increase in temperature is 3.3 °C.

Show that the heat energy change (Q) in this second experiment is approximately 700 J. [for water, c = 4.2 J/g/°C] [mass of 1.0 cm³ of water = 1.0 g]

In this experiment the student uses 1.70 g of the anhydrous copper(II) sulfate. Calculate the molar enthalpy change (ΔH) in kJ/mol. Include a sign in your answer. [Mr of CuSO₄ = 159.5] ΔH = kJ/mol

Another student does a similar experiment but uses hydrated copper(II) sulfate instead of anhydrous copper(II) sulfate. The table shows his results. initial temperature in °C 23.8 final temperature in °C when all solid dissolves 22.7 Explain what the results show about the type of energy change that occurs when hydrated copper(II) sulfate dissolves.

Sodium hydrogencarbonate (NaHCO₃) is also known as baking soda. Baking soda can be used to make cakes increase in size in an oven. This is the equation for the reaction that takes place when baking soda is heated. 2NaHCO₃(s) → Na₂CO₃(s) + CO₂(g) + H₂O(g)

What type of reaction is this?

Suggest why the reaction makes the cakes increase in size.

A student uses this apparatus to investigate the reaction that takes place when sodium hydrogencarbonate is heated. sodium hydrogencarbonate crucible pipeclay triangle heat This is the student’s method.

• weigh a crucible and record the mass
• add some sodium hydrogencarbonate to the crucible, reweigh it and record the mass
• heat the crucible and contents for five minutes, then allow to cool before weighing and recording the mass
• heat the crucible and contents again for a further three minutes, then allow to cool before weighing and recording the mass

Give a reason why the crucible and contents are heated for a further three minutes.

The student considered using a lid on the crucible in the experiment. Suggest an advantage and a disadvantage of using a lid on the crucible. advantage disadvantage

The table shows some of the student’s results. mass of crucible and sodium hydrogencarbonate in g 29.75 mass of empty crucible in g 26.50

Calculate the mass of sodium hydrogencarbonate that the student uses. mass = g

Using this equation, calculate the maximum mass of sodium carbonate (Na₂CO₃) that could form in the student’s reaction. 2NaHCO₃(s) → Na₂CO₃(s) + CO₂(g) + H₂O(g) [Mr of NaHCO₃ = 84 Mr of Na₂CO₃ = 106] maximum mass = g

In a second experiment, the student uses a larger mass of sodium hydrogencarbonate. She calculates that she should obtain 4.8 g of sodium carbonate. She actually obtains 4.2 g of sodium carbonate.

Calculate the percentage yield from the student’s experiment. percentage yield = %

Other than spillages, suggest a possible reason why the student’s actual yield is less than expected.

The table gives information about some lead compounds. Compound Formula Appearance Solubility in water lead(II) oxide PbO yellow solid insoluble lead(IV) oxide PbO₂ brown solid insoluble red lead oxide Pb₃O₄ red solid insoluble lead(II) nitrate Pb(NO₃)₂ white solid soluble

When a sample of red lead oxide is heated, it changes into a yellow solid and a gas forms that relights a glowing splint. Complete the word equation for this reaction. red lead oxide → +

A sample of one of the oxides of lead contains 86.6% lead and 13.4% oxygen by mass. Show by calculation that the sample is lead(IV) oxide, PbO₂ [Ar of Pb = 207 Ar of O = 16]

Red lead oxide reacts with warm dilute nitric acid.

Complete the chemical equation for the reaction. Pb₃O₄( ) + 4HNO₃( ) → Pb(NO₃)₂(aq) + PbO₂(s) + H₂O(l)

A student is given a sample of solid red lead oxide and some dilute nitric acid. Describe how the student could obtain a pure dry sample of lead(II) nitrate crystals.