Empirical formulae

This question is about organic compounds.

Chloroethene (C₂H₃Cl) is a covalent molecule that is used to make poly(chloroethene).

This is the displayed formula of chloroethene.

Draw a dot‑and‑cross diagram of chloroethene.

Show only the outer shell electrons.

Describe, in terms of electrostatic attraction, what is meant by a covalent bond.

Chloroethene is a monomer.

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

Poly(chloroethene) is non‑biodegradable.

There are two main methods used to dispose of poly(chloroethene).

Describe one problem caused by each method.

An organic compound contains this percentage composition by mass.

C = 22.0% H = 4.6% Br = 73.4%

Calculate the empirical formula of this compound.

Ethane and ethene undergo different types of reaction with bromine.

Describe the differences between these two reactions.

Magnesium sulfate crystals have the formula MgSO₄.xH₂O

A student uses this apparatus to heat tube A and collect water of crystallisation in tube B.

The student records the mass of tube B at the start and every minute for 6 minutes.

The table gives the student’s results.

Give a reason why the student surrounds tube B with ice.

State how the student knows when all the water of crystallisation has been given off.

Describe a chemical test the student can use to show that the liquid in tube B contains water.

The decomposition of hydrated magnesium sulfate is shown in the equation.

At the end of the reaction, the mass of MgSO₄ remaining in the tube is 6.0 g.

Use this mass and the results in the table to calculate x in MgSO₄.xH₂O

[for MgSO₄, M_r = 120 for H₂O, M_r = 18]

This question is about the reactions of some compounds of lead.

Lead can be extracted from lead(II) sulfide, PbS, in two stages.

Stage 1 lead(II) sulfide is heated in air and reacts with oxygen to produce lead(II) oxide, PbO, and sulfur dioxide

Stage 2 lead(II) oxide is heated with carbon in a furnace

Write a chemical equation for the reaction in stage 1.

Give a reason why sulfur dioxide should not be released into the atmosphere.

This is the equation for stage 2.

A mass of 892 tonnes of lead(II) oxide is heated in a furnace with an excess of carbon.

Calculate the maximum mass, in tonnes, of carbon dioxide that could be released into the atmosphere.

[1 tonne = 110⁶g]

[for PbO, M_r = 223 for CO₂, M_r = 44]

The diagram shows the structures of lead(II) sulfide and sulfur dioxide.

Explain, in terms of bonding and structure, why lead(II) sulfide is a solid with a very high melting point at room temperature and why sulfur dioxide is a gas at room temperature.

lead(II) sulfide

sulfur dioxide

A different oxide of lead contains 90.7% by mass of lead and 9.3% by mass of oxygen.

Determine the empirical formula of this oxide of lead.

This question is about the metal tantalum, Ta.

Tantalum metal can be produced by heating tantalum chloride (TaCl₅) and hydrogen gas in a furnace.

The other product of the reaction is hydrogen chloride.

Complete the equation for the reaction.

As tantalum chloride is heated, the mass of solid in the furnace decreases leaving tantalum as the only solid product.

The table shows the mass of solid in the furnace at one-hour intervals.

State how the data in the table shows that the reaction is complete.

Use the data to show that the formula of tantalum chloride is TaCl₅

[for tantalum, A_r = 181 for chlorine, A_r = 35.5]

QUESTION 12 CONTINUES ON NEXT PAGE.

Another method of extracting tantalum is by reacting tantalum(V) oxide with carbon.

This is the equation for the reaction.

Explain why this is a redox reaction.

2000 mol of tantalum(V) oxide is heated with 500 000 g of carbon.

Show by calculation that the carbon is in excess.

[for carbon, A_r = 12]

Calculate the maximum mass, in grams, of tantalum that can be obtained from 2000 mol of tantalum(V) oxide.

[for tantalum, A_r = 181]

Sodium sulfate can be prepared by the reaction between sodium hydroxide solution and sodium hydrogensulfate (NaHSO₄) solution.

This is the equation for the reaction.

Sodium hydrogensulfate solution is acidic.

A student adds 25.0 cm³ of sodium hydroxide solution to a conical flask and adds two drops of indicator.

The student does a titration.

Name a piece of apparatus that should be used to add 25.0 cm³ of sodium hydroxide solution to the conical flask.

Describe the method the student should use to find the accurate volume of sodium hydrogensulfate solution needed to neutralise the 25.0 cm³ of sodium hydroxide solution.

The student repeats the titration without the indicator and forms a solution of sodium sulfate.

Describe how the student can obtain pure, dry crystals of hydrated sodium sulfate from the solution.

Crystals of hydrated sodium sulfate decompose when heated.

This is the equation for the decomposition.

A student uses this apparatus to find the value of x.

The student heats the crystals until the decomposition is complete.

The table shows the student’s results.

Use the results to calculate the value of x.

[for Na₂SO₄, M_r = 142 for H₂O, M_r = 18]

This question is about alkanes and alkenes.

The alkane C₄H₁₀ exists as two isomers.

State what is meant by the term isomers.

Draw the displayed formulae for the two isomers of C₄H₁₀

Ethane (C₂H₆) can react with bromine.

State the condition needed for ethane to react with bromine.

Complete the equation for this reaction.

Give the name for this type of reaction.

Explain why ethane is described as a saturated compound.

State what you would observe when ethane and ethene are added separately to two samples of bromine water.

ethane

ethene

Explain why straight‑chain alkenes always have the same empirical formula, but straight‑chain alkanes have different empirical formulae.

Refer to the molecular formulae of the alkanes C₂H₆ and C₄H₁₀ in your answer.

An organic compound has this percentage composition by mass.

C = 19.2 % H = 4.0 % O = 12.8 % Br = 64.0 %

Calculate the empirical formula of this compound.

A scientist uses this apparatus in an experiment to reduce a metal oxide to a metal.

Before heating the mass of the empty tube and the mass of the tube and the metal oxide are recorded.

After heating, the tube is allowed to cool and the mass of the tube and its contents is recorded again.

State why the reaction of the metal oxide to form a metal is described as a reduction reaction.

State why it is important to relight the hydrogen at the end of the tube if the flame goes out.

Explain why it is important to continue passing hydrogen into the tube and burning the hydrogen at the end of the tube until the contents have cooled.

Describe what should be done next to ensure that all the metal oxide has been converted into the metal.

In this experiment a mass of 4.14 g of metal is formed from 4.46 g of the metal oxide.

Calculate the amount, in moles, of oxygen atoms in the sample of the metal oxide.

The formula of the metal oxide is MO, where M represents the symbol of the metal.

Deduce the amount, in moles, of M in the sample of the metal oxide.

Calculate the relative atomic mass of M.

Use the Periodic Table to identify metal M.

This question is about mixtures and compounds.

The box gives some techniques used to separate mixtures.

The table lists some substances and mixtures.

Complete the table using words from the box to show the best technique to obtain the named substance from each mixture.

Each technique may be used once, more than once or not at all.

State how the box represents a mixture.

Food colourings are mixtures of food dyes.

A student uses paper chromatography to separate the food dyes contained in food colouring D.

The student places spots of three food dyes A, B and C and food colouring D on chromatography paper.

The diagram shows the appearance of the paper after the experiment.

Describe the composition of food colouring D.

A compound has the formula Ca(HCO₃)₂

Determine the number of different elements in Ca(HCO₃)₂

Determine the number of atoms in the formula of Ca(HCO₃)₂

This question is about unsaturated hydrocarbons.

Ethene (C₂H₄) is a member of the homologous series of alkenes.

Give two characteristics of a homologous series.

Draw a dot-and-cross diagram to show the bonding in a molecule of ethene.

Show outer electrons only.

Propene (C₃H₆) is another member of the homologous series of alkenes.

State why the empirical formula of all alkenes in this homologous series is CH₂

Propene can be polymerised to form poly(propene).

Draw the displayed formula of propene and the repeat unit of poly(propene).

propene
repeat unit of poly(propene)

This is the structural formula of another hydrocarbon compound.

Give the molecular formula and the empirical formula of this compound.

molecular formula

empirical formula

Explain why this compound is an unsaturated hydrocarbon.

Describe a test to show that this hydrocarbon is unsaturated.

This question is about different hydrated forms of sodium sulfate.

A compound has the formula Na₂SO₄.7H₂O

How many different elements are there in the formula Na₂SO₄.7H₂O?

What is the total number of atoms in the formula Na₂SO₄.7H₂O?

Another hydrated form of sodium sulfate has the formula Na₂SO₄.xH₂O

A student uses this apparatus to find the value of x.

This is the student’s method.

• find the mass of an empty tube

• add solid hydrated sodium sulfate to the tube

• find the mass of the tube and hydrated sodium sulfate

• heat the tube for several minutes

• allow the tube to cool and find the mass of the tube and contents

Describe what the student should do next to make sure that all the water is removed from the hydrated sodium sulfate.

Explain the role of the ice in the beaker.

Describe how the student could prove that the liquid collected is pure water.

The table gives the student’s results.

Use the student’s results to calculate the value of x.

[for Na₂SO₄, M_r = 142 for H₂O, M_r = 18]

This question is about propene.

The structural formula of propene is CH₃CH CH₂

Complete the dot-and-cross diagram for a molecule of propene.

Describe the forces of attraction that hold the atoms together in a molecule of propene.

The alkane pentadecane has the formula C₁₅H₃₂

Describe how propene can be produced from pentadecane.

Propene is used to make poly(propene).

Complete the equation for the formation of poly(propene).

Explain why the disposal of poly(propene) in landfill sites is a problem.

Propene can be converted into compound X.

Compound X contains these percentages by mass.

• carbon 60%

• hydrogen 13.3%

• oxygen 26.7%

Compound X has an M_r of 60

Determine the molecular formula of compound X.

Propene and compound X both have simple molecular structures.

Explain why compound X has a higher boiling point than propene.

This question is about alcohols.

Ethanol can be manufactured using two different methods.

• hydration of ethene

• fermentation of glucose

This is the equation for hydration.

Complete the equation for fermentation.

The table gives some information about the two methods.

Complete the table by giving the missing information.

Explain one advantage and one disadvantage of using fermentation rather than hydration to produce ethanol.

You should use information from the table to help your answer.

advantage

disadvantage

Explain why fermentation needs to occur in the absence of air.

Propanol has this percentage composition by mass.

C = 60.0% H = 13.3% O = 26.7%

Show by calculation that the empirical formula of propanol is C₃H₈O.

Draw the displayed formula of propanol.

This question is about organic compounds.

Give the total number of atoms in one molecule of methanoic acid.

Determine the relative molecular mass (M_r) of methanoic acid.

Explain why methanoic acid is not a hydrocarbon.

The atoms in methanoic acid are held together by covalent bonds.

State, in terms of electrostatic attractions, what is meant by the term covalent bond.

Draw a dot‑and‑cross diagram to show the bonding in a molecule of methanoic acid.

Show only the outer electrons of each atom.

Calculate the empirical formula of the organic compound with this composition by mass.

C = 52.2% H = 13.0% O = 34.8%

This question is about polymers.

This is the structure of a monomer.

What is the name of this monomer?

Complete the equation to show the repeat unit of the polymer that forms from this monomer.

A typical molecule of the polymer has a relative molecular mass (M_r) of 2 490 000

Show that the number of monomer molecules needed to make this typical molecule is about 40 000

[for C, A_r = 12 for Cl, A_r = 35.5]

These are two methods used to dispose of the polymer.

• burying in landfill sites

• burning

Discuss the environmental problems caused by these two methods of disposal.

A different polymer molecule contains 10 600 atoms of carbon, 10 600 atoms of hydrogen and 31 800 atoms of chlorine.

Determine the empirical formula of this polymer.

A teacher ignites a piece of magnesium ribbon and places it in a gas jar of oxygen.

This is the equation for the reaction.

Give two observations that would be made during this reaction.

The teacher demonstrates the reaction between aluminium and iron(III) oxide.

The teacher ignites the magnesium fuse. A very exothermic reaction then occurs between aluminium powder and iron(III) oxide.

The products of the reaction are iron and aluminium oxide.

State what is meant by the term exothermic.

Give a chemical equation for the reaction between aluminium and iron(III) oxide.

Explain why this reaction is a redox reaction.

A student uses this apparatus to determine the formula of magnesium oxide.

This is the student’s method.

• find mass of empty crucible and lid

• place some magnesium ribbon in crucible

• find mass of crucible, lid and magnesium ribbon

• heat crucible, lifting lid occasionally

• after five minutes, find mass of crucible, lid and magnesium oxide

Explain why the student lifts the lid.

The mass of magnesium oxide formed is less than expected.

Describe what the student should do next to obtain a more accurate value for the mass of magnesium oxide.

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 record mass of tube A when empty

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

Step 3 heat tube A

Step 4 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

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

Calculate the mass of BaCl₂ that forms in tube A.

Calculate the mass of water lost.

Determine the value of x in BaCl₂. xH₂O

Show your working.

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

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

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.

Give the meaning of the symbol

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

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 610²³ particles.

This question is about metals.

Explain why metals are malleable.

Explain why molten sodium chloride conducts electricity.

Explain how sodium metal forms at the negative electrode.

Write an ionic half-equation for the formation of chlorine gas at the positive electrode.

Give a reason why sodium metal does not form in the electrolysis of an aqueous solution of sodium chloride.

Copper can be produced by reacting an oxide of copper with methane.

The diagram shows the apparatus used.

The oxide of copper is heated until the reaction is complete.

The table shows the results.

Use the results to show that this oxide has the empirical formula CuO

[for Cu, A_r = 63.5 for O, A_r = 16]

This question is about copper and copper compounds.

A sample of copper contains two isotopes.

• Cu-63 with relative abundance 69.5%

• Cu-65 with relative abundance 30.5%

State what is meant by the term isotopes.

Calculate the relative atomic mass (A_r) of this sample of copper.

Give your answer to three significant figures.

When copper(II) carbonate is heated, copper(II) oxide and carbon dioxide are formed.

What is the name of this type of reaction?

Which colour change occurs during this reaction?

A student uses this apparatus to find the value of x in the formula CuSO₄.xH₂O

This is the student’s method.

• find the mass of an empty boiling tube

• add hydrated copper(II) sulfate to the tube and record the new mass

• heat the hydrated copper(II) sulfate until it changes colour

• allow the tube to cool and record the mass again

The table shows the student’s results.

Calculate the mass of CuSO₄ formed.

Calculate the mass of water formed.

Show that the value of x is approximately 4

[M_r of CuSO₄ = 159.5 M_r of H₂O = 18]

The actual value of x is 5

Give a reason why the calculated value of x is lower than the actual value.

A teacher uses this apparatus to reduce tungsten oxide.

This is the teacher’s method.

• record the mass of a weighing boat

• add tungsten oxide and record the mass again

• heat the weighing boat and tungsten oxide strongly for two minutes and then allow to cool

• record the mass of the weighing boat and its contents

Complete the equation by adding the state symbols.

Give an addition to the method to check that the tungsten oxide has been completely reduced.

The table shows the teacher’s results.

Use the teacher’s results to show that the empirical formula of tungsten oxide is WO₃

[for tungsten, A_r = 184 for oxygen, A_r = 16]

The teacher wears eye protection and a lab coat during the experiment.

Give one other safety precaution the teacher should take.

In industry, tungsten oxide is reduced on a large scale using hydrogen.

The percentage yield of tungsten is 73.5%

This is the equation for the reaction.

Calculate the mass, in tonnes, of tungsten that is produced when 2784 tonnes of tungsten oxide are reacted with an excess of hydrogen.

[1 tonne = 110⁶g]

[for tungsten, A_r = 184 for oxygen, A_r = 16]

mass of tungsten =_........ tonnes

This question is about alkanes.

Which of these is the molecular formula of an alkane?

Which of these has the same empirical formula and molecular formula?

In the presence of ultraviolet radiation, methane reacts with bromine to form bromomethane and hydrogen bromide.

State the name of this type of reaction.

Give a chemical equation for this reaction.

One mole of an alkane burns completely in oxygen.

The equation represents the reaction.

The numbers x, y and z are used to balance the equation.

The complete combustion of one mole of the alkane produces 220 g of carbon dioxide and 108 g of water.

Calculate the values of y and z.

[M_r of CO₂ = 44 M_r of H₂O = 18]

Determine the molecular formula of the alkane and the value of x.

When an alkane burns in a limited supply of air, incomplete combustion occurs.

Explain why incomplete combustion of an alkane could be harmful to humans.

This question is about alcohols, carboxylic acids and esters.

Ethanol can be manufactured by the fermentation of a solution of glucose.

Write a word equation for this reaction.

State the substance that needs to be added for the reaction to occur.

State two conditions needed for this reaction.

In the presence of an acid catalyst, ethanoic acid is heated with butanol to form an ester.

Which of these is the formula of the ester?

State how you would know that an ester has formed.

Give one use of an ester.

Aspirin is a compound used to reduce pain.

Aspirin contains a carboxylic acid functional group and an ester functional group.

State what is meant by the term functional group.

This is the structural formula of aspirin.

O O

Draw a circle around the carboxylic acid functional group.

Aspirin has this percentage composition by mass.

C = 60.00 % H = 4.44 % O = 35.56 %

Show by calculation that the empirical formula of aspirin is C₉H₈O₄

An organic compound has this percentage composition by mass.

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

Show that the empirical formula of the compound is CH₂O

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

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

Complete the equation for this reaction.

2HCOOH + Na₂CO_{3 ........} +_........ +_........

State what you would observe in this reaction.

Methanoic acid also reacts with propanol to form an ester.

The equation for the reaction is

Give the name of the ester that forms.

State what is meant by the symbol.

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

Give one characteristic of a reaction at dynamic equilibrium.

A polyester forms when butanedioic acid reacts with ethanediol.

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

O O

Give the name of this type of polymerisation.

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

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

Give the letter of a saturated compound with the general formula C_nH_2n

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.

Give the name of this type of reaction.

Another compound, G, has this percentage composition by mass.

C = 37.8 % H = 6.3 % C l = 55.9 %

Show by calculation that the empirical formula of compound G is C₂H₄Cl

The relative formula mass (M_r) of G is 127

Determine the molecular formula of G.

Compound E is used to make an addition polymer.

Give one problem caused by the disposal of addition polymers.

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

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]

[M_r of ZnSO₄·7H₂O = 287 M_r of H₂O = 18]

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.

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

This question is about salts.

Soluble salts can be prepared by the reaction between a metal oxide and an acid.

The equation for this type of reaction is

metal oxide + acid salt + water

State the name given to this type of reaction.

State, in terms of protons, what happens in this reaction.

A student is given 50 cm³ of dilute sulfuric acid and a bottle of solid copper(II) carbonate.

Describe the method that the student should use to prepare a saturated solution of copper(II) sulfate.

In your answer, refer to the pieces of apparatus that the student should use.

The student produces dry crystals of hydrated copper(II) sulfate from the saturated solution.

He calculates that 6.40 g of dry crystals should be formed.

The mass of dry crystals he actually obtains is 1.80 g less than he calculated.

Calculate the student’s percentage yield.

Give your answer to one decimal place.

Gypsum is hydrated calcium sulfate.

A sample of gypsum contains 79% of calcium sulfate by mass.

Calculate the value of x in CaSO₄.xH₂O

Describe a test for calcium ions in the sample of gypsum.

The diagram shows the displayed formula of the organic compound methanol, CH₃OH

Determine the number of atoms in one molecule of methanol.

State why methanol is not a hydrocarbon.

The atoms in methanol are held together by covalent bonds.

State what is meant by the term covalent bond.

Draw a dot-and-cross diagram to show the bonding in a molecule of methanol.

Show only the outer electrons of each atom.

Another organic compound has the percentage composition by mass

C = 38.7% H = 9.7% O = 51.6%

Calculate the empirical formula of this compound.

The relative molecular mass (M_r) of the compound is 62

Determine the molecular formula of the compound.

The table shows the molecular formulae of six organic compounds, A, B, C, D, E and F.

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.

A piece of magnesium ribbon is ignited and placed in a gas jar of oxygen.

The equation for the reaction is

Give two observations that would be made in this reaction.

State why this is an oxidation reaction.

A second piece of magnesium ribbon is ignited and placed in a gas jar of carbon dioxide.

A very exothermic reaction occurs, forming magnesium oxide and carbon.

State what is meant by the term exothermic.

Give the chemical equation for this reaction.

A fire starts in a warehouse where magnesium is stored.

Suggest why it would not be suitable to use a carbon dioxide fire extinguisher to put out this fire.

A student uses this apparatus to find the mass of magnesium oxide that forms when a known mass of magnesium is heated.

This is his method.

• find the mass of the crucible and lid

• place some magnesium ribbon in the crucible

• find the mass of the crucible, lid and magnesium

• heat the crucible with the lid on for a few minutes

• find the mass of the crucible, lid and magnesium oxide

Using this method, the mass of magnesium oxide formed is less than expected.

Explain two changes that the student should make to his method to obtain a mass of magnesium oxide closer to the expected mass.

The table gives information about some lead compounds.

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

[A_r of Pb = 207 A_r 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.

The boxes show the displayed formulae of six organic compounds, P, Q, R, S, T and U.

Use the letters P, Q, R, S, T and U to answer these questions.

Each letter may be used once, more than once or not at all.

Give the letter of the compound that is not a hydrocarbon.

Give the letters of the two compounds that have the same empirical formula.

Give the letter of the compound that is used to manufacture poly(propene).

Describe a test that can be used to distinguish between compounds Q and T.

result with compound Q_........

result with compound T_........

Compounds P, Q and R are members of the same homologous series.

Give two characteristics of a homologous series.

This is the displayed formula of an alkene, V.

Give the name of alkene V.

Draw the displayed formula of another alkene that is an isomer of alkene V.

An organic compound has the percentage composition by mass

C = 36.36% H = 6.06% F = 57.58%

Show that the empirical formula of the compound is CH₂F

The relative molecular mass (M_r) of the compound is 66.

Determine the molecular formula of the compound.

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(_........ ) _........ Cu(_........ ) +_........ CO₂(_........ ) +_........ H₂O(_........

A teacher uses this apparatus to demonstrate the reaction between a different oxide of copper and methane.

The teacher heats the oxide of copper until the reaction is complete.

The table shows the teacher’s results.

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

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]

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.

This question is about copper and its compounds.

Copper is a metal used for electrical wiring.

Explain why copper is a good conductor of electricity.

This apparatus is used to investigate the electrolysis of copper(II) sulfate solution with graphite electrodes.

Copper forms at the negative electrode and oxygen forms at the positive electrode.

State what would be observed at each electrode.

negative electrode_........

positive electrode_........

The ionic half‑equation for the reaction at the negative electrode is

State why this is a reduction reaction.

Explain why the copper(II) sulfate solution becomes paler blue during the electrolysis.

When hydrated copper(II) sulfate crystals are heated, anhydrous copper(II) sulfate forms.

A mass of 12.5 g of hydrated copper(II) sulfate crystals is heated in a crucible until all the water of crystallisation is removed.

A mass of 8.0 g of anhydrous copper(II) sulfate forms.

Show by calculation that the formula of hydrated copper(II) sulfate is CuSO₄.5H₂O

[M_r of CuSO₄ = 159.5 M_r of H₂O = 18]