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Reversible reactions

Edexcel IGCSE Chemistry

Topic questions The rate and extent of chemical change Reversible reactions

Reversible reactions

6 questions · 70 marks · about 1.5 hours

Reversible reactions questions

TopicReversible reactions

Chemistry Paper 1 January 2023, Question 12 13 marks

This question is about hydrated compounds.

Crystals of hydrated barium chloride (BaCl₂. xH₂O) contain water of crystallisation.

A student uses this apparatus to remove and collect the water from some crystals.

This is the student’s method.

Step 1 maths symbol record mass of tube A when empty

Step 2 maths symbol place a sample of hydrated barium chloride crystals in tube A and record new mass

Step 3 maths symbol heat tube A

Step 4 maths symbol allow tube A to cool and record mass

Repeat steps 3 and 4 until the mass recorded in step 4 is constant.

These are the student’s results.

mass of tube A = 10.55 g

mass of tube A and BaCl₂. xH₂O = 16.65 g

final mass of tube A and BaCl₂ = 15.75 g

(a)(i)

Give a reason why the student repeats steps 3 and 4 until the mass is constant.

[1]

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(a)(ii)

Calculate the mass of BaCl₂ that forms in tube A.

[1]

(a)(iii)

Calculate the mass of water lost.

[1]

(a)(iv)

Determine the value of x in BaCl₂. xH₂O

Show your working.

[for BaCl₂, M_r = 208 for H₂O, M_r = 18]

[3]

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(b)

Describe a physical test to show that the water in tube B is pure.

[2]

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(c)

A sample containing 0.02 mol of hydrated copper(II) sulfate is heated using the same apparatus.

The products of the reaction are anhydrous copper(II) sulfate and water.

This is the equation for the reaction.

$Question 12, shown as an image$

(c)(i)

Give the meaning of the symbol maths symbol

[1]

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(c)(ii)

Describe how the reaction can be used to show that a liquid contains water.

[2]

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(c)(iii)

Calculate the maximum number of water molecules in tube B after the sample of hydrated copper(II) sulfate has completely reacted.

One mole of any substance contains 6 maths symbol 10²³ particles.

[2]

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Chemistry Paper 2 June 2022, Question 5 12 marks

(a)

An organic compound has this percentage composition by mass.

C = 40 % H = 6.7 % O = 53.3 %

(a)(i)

Show that the empirical formula of the compound is CH₂O

[2]

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(a)(ii)

Draw the structural formula of a compound with the molecular formula C₂H₄O₂

[1]

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(b)

Methanoic acid (HCOOH) reacts with sodium carbonate solution to give three products.

(b)(i)

Complete the equation for this reaction.

2HCOOH + Na₂CO₃ maths symbol _........ +_........ +_........

[2]

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(b)(ii)

State what you would observe in this reaction.

[1]

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(c)

Methanoic acid also reacts with propanol to form an ester.

The equation for the reaction is

$Question 5, shown as an image$

(c)(i)

Give the name of the ester that forms.

[1]

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(c)(ii)

State what is meant by the maths symbol symbol.

[1]

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(c)(iii)

When this reaction occurs in a sealed container, the reaction can reach dynamic equilibrium.

Give one characteristic of a reaction at dynamic equilibrium.

[1]

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(d)

A polyester forms when butanedioic acid reacts with ethanediol.

The diagram shows the repeat unit of the polyester that forms.

O O

$Question 5, shown as an image$

(d)(i)

Give the name of this type of polymerisation.

[1]

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(d)(ii)

Draw the structural formulae of the two monomers used to make this polyester.

[2]

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Chemistry Paper 2 June 2022 (R), Question 7 15 marks

Also involves Limiting reactants · Percentage yield · The Haber process

In the presence of an iron catalyst, nitrogen reacts with hydrogen to form ammonia.

The reaction conditions used are a temperature of 450 maths symbol C and a pressure of 200 atmospheres.

This is the equation for the reaction.

$Question 7, shown as an image$

(a)(i)

State what the symbol maths symbol represents.

[1]

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(a)(ii)

Give the reason for using a catalyst.

[1]

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(b)(i)

The reaction mixture is kept at a pressure of 200 atmospheres, but the

$Question 7, shown as an image$

Explain the effect of this change on the yield of ammonia at equilibrium.

[2]

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(b)(ii)

The reaction mixture is kept at a temperature of 450 maths symbol C, but the pressure is increased to 300 atmospheres.

Explain the effect of this change on the yield of ammonia at equilibrium.

[2]

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(c)

Draw an energy level diagram for the reaction between nitrogen and hydrogen.

Include the reactants, products and Δ H in your diagram.

[3]

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(d)

QUESTION 7 CONTINUES ON NEXT PAGE

At the start of the reaction, 48 dm³ of nitrogen is added to 120 dm³ of hydrogen at rtp.

$Question 7, shown as an image$

[molar volume of any gas at rtp = 24 dm³]

(d)(i)

Show by calculation that the nitrogen is in excess.

[3]

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(d)(ii)

The yield of ammonia at equilibrium is 20 %.

Calculate the volume, in dm³, of ammonia formed from 120 dm³ of hydrogen.

[3]

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Chemistry Paper 1 January 2020 (R), Question 4 9 marks

This question is about ammonium chloride.

(a)

Give the formula of the ammonium ion.

[1]

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(b)

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

[3]

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(c)

The equation shows the thermal decomposition of ammonium chloride.

$Question 4, shown as an image$

State what the maths symbol symbol indicates about this reaction.

[1]

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(d)

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

(d)(i)

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

[2]

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(d)(ii)

Gas particles travel very quickly.

Give two reasons why it takes several minutes for the ammonium chloride to form.

[2]

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Chemistry Paper 1 January 2020, Question 10 12 marks

Also involves Moles and amount of substance

(a)(i)

Complete the chemical equation for the reaction in stage 1.

$Question 10, shown as an image$

[1]

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(a)(ii)

Give the meaning of the symbol maths symbol

[1]

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(a)(iii)

State the purpose of the platinum catalyst.

[1]

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(b)

Give a chemical equation for the reaction of nitrogen monoxide and oxygen in stage 2.

[1]

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(c)

(c)(i)

The equation for the reaction in stage 3 is

$Question 10, shown as an image$

Calculate the maximum mass, in tonnes, of nitric acid that could be produced in this reaction from 11.5 tonnes of nitrogen dioxide.

$Question 10, shown as an image$

mass of nitric acid =_........ tonnes

[4]

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(c)(ii)

Suggest what use can be made of the nitrogen monoxide gas formed in stage 3.

[1]

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(d)

When copper(II) oxide reacts with dilute nitric acid, copper(II) nitrate is produced.

The equation for the reaction is

$Question 10, shown as an image$

0.200 mol of nitric acid reacts with excess copper(II) oxide.

A mass of 15.3 g of copper(II) nitrate is produced.

Calculate the percentage yield of copper(II) nitrate.

[M_r of copper(II) nitrate = 187.5]

[3]

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Chemistry Paper 2 June 2019 (R), Question 7 9 marks

Also involves Moles and amount of substance

Hydrogen gas can be produced by reacting a mixture of methane and steam in the presence of a nickel catalyst.

The reaction conditions are a temperature of 700 maths symbol C and a pressure of 5 atmospheres.

The equation for the reaction is

$Question 7, shown as an image$

(a)

What does the symbol maths symbol represent?

[1]

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(b)(i)

The mixture of methane and steam is heated to a temperature greater than 700 °C but the pressure is kept at 5 atmospheres.

Predict the effect of this change on the yield of hydrogen at equilibrium, giving a reason for your answer.

[2]

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(b)(ii)

The mixture of methane and steam is kept at the same temperature of 700 °C but the pressure is increased to more than 5 atmospheres.

Predict the effect of this change on the yield of hydrogen at equilibrium, giving a reason for your answer.

[2]

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(c)

Calculate the volume, in dm³, of hydrogen gas at rtp that is produced when 10 tonnes of methane gas completely react with steam.

[molar volume of hydrogen at rtp is 24 dm³]

Give your answer in standard form.

[4]

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Memes

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Laugh now. Cry in the exam hall later. Then come back and do a past paper.

Do the mole calculation

Write ‘exothermic’ and pray

Me on the 6-marker about electrolysis

Knowing water is H₂O

Balancing an equation first try

Getting two concordant titres

Realising nobody actually knows what a mole is

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Reversible reactions

Reversible reactions questions

Edexcel 4CH1 Reversible reactions 6 questions

Chemistry Paper 1 January 2023, Question 12 Chemistry Paper 1 · January 2023 · Question 12 13 marks

Chemistry Paper 2 June 2022, Question 5 Chemistry Paper 2 · June 2022 · Question 5 12 marks

Chemistry Paper 2 June 2022 (R), Question 7 Chemistry Paper 2 · June 2022 (R) · Question 7 15 marks

Chemistry Paper 1 January 2020 (R), Question 4 Chemistry Paper 1 · January 2020 (R) · Question 4 9 marks

Chemistry Paper 1 January 2020, Question 10 Chemistry Paper 1 · January 2020 · Question 10 12 marks

Chemistry Paper 2 June 2019 (R), Question 7 Chemistry Paper 2 · June 2019 (R) · Question 7 9 marks

Certified Chemistry memes. Peer-reviewed by nobody.

Chemistry Paper 1 January 2023, Question 12 13 marks

Chemistry Paper 2 June 2022, Question 5 12 marks

Chemistry Paper 2 June 2022 (R), Question 7 15 marks

Chemistry Paper 1 January 2020 (R), Question 4 9 marks

Chemistry Paper 1 January 2020, Question 10 12 marks

Chemistry Paper 2 June 2019 (R), Question 7 9 marks