Atmospheric pollutants

Butane (C₄H₁₀) is an alkane.

Explain why butane is a saturated hydrocarbon.

When butane 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.

One product of the incomplete combustion of butane is carbon monoxide.

Give the name of another product of this incomplete combustion.

State why carbon monoxide is poisonous to humans.

C₄H₁₀ exists as two isomers.

State what is meant by the term isomers.

Draw the displayed formula of each isomer.

Explain why hexane (C₆H₁₄) has a higher boiling point than butane (C₄H₁₀).

This question is about gases.

The box gives the names of some gases.

Choose gases from the box to answer questions (i) to (iv).

You may use each gas once, more than once or not at all.

Identify two gases in Group 0 of the Periodic Table.

Identify the gas that makes up about 21% of the atmosphere.

Identify a greenhouse gas.

Identify the toxic gas formed by incomplete combustion of a hydrocarbon.

Describe a test to show that a gas is carbon dioxide.

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 methane, CH₄

The diagram shows a Bunsen burner that uses methane.

During combustion, methane reacts with a gas in the air.

Give the name of this gas.

Give the two products of the complete combustion of methane.

During the incomplete combustion of methane, carbon monoxide forms.

Give a reason why carbon monoxide forms during incomplete combustion.

State why carbon monoxide is poisonous.

The equation shows the reaction of methane with bromine.

Give the name of this type of chemical reaction.

This question is about crude oil.

Describe how crude oil is separated into fractions by fractional distillation.

Some of the products of fractional distillation are then cracked.

This equation represents a reaction that occurs during cracking.

Explain why cracking is an important process in the oil industry.

Fuels obtained from crude oil may contain impurities.

Explain how an impurity found in fuels can cause an environmental problem.

Methane reacts with steam to form carbon monoxide and hydrogen.

This is the equation for the reaction.

State why carbon monoxide is poisonous to humans.

Explain the effect, if any, on the yield of hydrogen at equilibrium when a nickel catalyst is used.

The reaction conditions for this reaction are a temperature of 700 °C and a pressure of 5 atmospheres.

The temperature of the reaction mixture is reduced to 600 °C, but the pressure is kept at 5 atmospheres.

Explain the effect on the yield of hydrogen at equilibrium.

The pressure of the reaction mixture is reduced to 4 atmospheres, but the temperature is kept at 700 °C.

Explain the effect on the yield of hydrogen at equilibrium.

Calculate the volume, in dm³, of methane gas at rtp needed to produce 6.6 tonnes of hydrogen gas.

[at rtp, molar volume = 24 dm³ 1 tonne = 10⁶g]

Give your answer in standard form.

This question is about alkanes.

An alkane has the structural formula CH₃CH₂CH₂CH₃

Give the missing information for this alkane.

There are two isomers of C₄H₁₀

State what is meant by the term isomers.

Draw the displayed formula of each isomer of C₄H₁₀

Isomer 1
Isomer 2

Methane reacts with bromine to form bromomethane and one other product.

Give the formula of the other product.

What is the name of this type of reaction?

State the condition needed for this reaction to occur.

When ethane (C₂H₆) burns in a plentiful supply of air, carbon dioxide and water are formed.

Give a chemical equation for this reaction.

When the air supply is limited, incomplete combustion occurs.

Explain why a gas formed by incomplete combustion can cause a problem for humans.

Give a reason why compound X is not a hydrocarbon.

Give the letter of the compound that is a saturated hydrocarbon with the empirical formula CH₂

Give the letter of the compound that produces nine moles of water when one mole undergoes complete combustion.

Give the structural formula of compound Y.

Explain why compounds W and Y are isomers.

Compound Z reacts with bromine in the presence of ultraviolet radiation.

Write a chemical equation for this reaction.

What is the name for this type of reaction?

Describe how the combustion of sulfur-free petrol in a car engine produces gases that can cause acid rain.

Do not refer to carbon dioxide in your answer.

When 10.0 kg of a solid fuel is burned, the heat energy produced is 3.28 × 10⁵kJ.

Calculate the heat energy, in kJ/mol, produced by the fuel.

You should assume that the fuel is pure carbon.

Give your answer to three significant figures.

[for carbon, A_r = 12]

heat energy =_........ kJ/mol

The fuel actually contains some impurities, including sulfur.

There is 600 g of sulfur in 20 kg of fuel.

Calculate the percentage of sulfur in the fuel.

When the fuel burns, the 600 g of sulfur produces sulfur dioxide gas.

Calculate the volume, in cm³, of sulfur dioxide gas that would be produced at room temperature and pressure (rtp) when the fuel burns.

[for a gas, molar volume = 24 dm³ at rtp]

State the name of the environmental problem caused by sulfur dioxide in the atmosphere.

Crude oil is an important source of organic compounds.

The diagram shows how crude oil can be separated into fractions by fractional distillation.

State what happens to the crude oil when it is in X.

Give the name of fraction E.

Give a use for fraction A.

One of the compounds in fraction D is tridecane (C₁₃H₂₈) which can be cracked to form shorter-chain hydrocarbons.

State the catalyst and temperature used in this cracking reaction.

catalyst

temperature

The equation shows an example of a catalytic cracking reaction.

Give two reasons why this reaction is important.

Sulfur is an impurity in crude oil. Explain why this is a problem for the environment.

This question is about ammonia and ammonium compounds.

Ammonia (NH₃) is a simple covalent molecule.

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

The table shows the names and formulae of some ammonium compounds.

Complete the table by giving the missing information.

When ammonia reacts with sulfuric acid, ammonium sulfate is formed.

Write a chemical equation for this reaction.

Describe a test for ammonium ions.

The table gives some information about ammonia and ammonium compounds.

Calculate the percentage of nitrogen in ammonium nitrate.

[M_r of NH₄NO₃ = 80]

Fertilisers add nitrogen to the soil to help plants grow.

Ammonia and ammonium sulfate can both be used as fertilisers.

Discuss the advantages and disadvantages of using each of these compounds as fertilisers.

Use information from the table in your answer.

[pH of rainwater is approximately 5.6]

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 gases in the air.

The pie chart represents the percentages of gases in dry, unpolluted air.

Gases with percentages of less than 1% in air are called trace gases.

Which of these is gas Z?

Which of these is the approximate percentage of oxygen in dry, unpolluted air?

One of the trace gases is carbon dioxide.

Identify two reactions that produce carbon dioxide by placing a tick (✓) in two boxes.

Name an environmental problem that is caused by the percentage of carbon dioxide increasing in the atmosphere.

Name the trace gas with the highest percentage in dry, unpolluted air.

Rainwater is acidic because carbon dioxide dissolves in water to form carbonic acid.

Acid rain is more acidic than rainwater because acidic pollutant gases also dissolve in water.

Give the name of the acid that forms when nitrogen dioxide dissolves in water.

Name another pollutant gas that also forms acid rain.

This question is about three stages in the manufacture of sulfuric acid.

In stage 1, sulfur is burned in oxygen to form sulfur dioxide gas.

State one environmental problem caused by the release of sulfur dioxide into the atmosphere.

A mass of 6.4 tonnes of sulfur is burned to produce sulfur dioxide gas.

Calculate the maximum volume, in dm³, of sulfur dioxide gas that can be produced at rtp.

[molar volume of sulfur dioxide gas at rtp = 24 dm³]

[1 tonne = 10⁶g]

Give your answer in standard form.

In stage 2, sulfur dioxide is reacted with oxygen to form sulfur trioxide gas.

The yield of sulfur trioxide is approximately 98%.

A catalyst is used in this reaction.

Explain how a catalyst increases the rate of a reaction.

The temperature is kept constant.

Give a reason why increasing the pressure would increase the yield of sulfur trioxide.

Suggest why it is not necessary to increase the pressure in stage 2.

In stage 3, the sulfur trioxide is reacted with concentrated sulfuric acid to form a liquid called oleum, H₂S₂O₇

The oleum is then added to water to form concentrated sulfuric acid.

Complete the chemical equations for these two reactions.

Sulfuric acid reacts with ammonia to form ammonium sulfate, (NH₄)₂SO₄

Calculate the percentage by mass of nitrogen in ammonium sulfate.

[M_r of (NH₄)₂SO₄ = 132]

Crude oil is a mixture of organic compounds.

Most of these compounds are members of the same homologous series.

State the name of this homologous series.

An industrial process is used to separate crude oil into fractions.

The process depends on a difference in a property of the fractions.

What is this property?

The boxes give some uses of fractions and some names of fractions.

Draw one straight line from each use to its correct fraction.

Fuels obtained from the fractions may contain impurities.

Explain how the combustion of a common impurity in fuels may cause an environmental problem.

Some of the fractions contain long-chain molecules which are not very useful.

Give the name of the process used to convert long-chain molecules into more useful shorter-chain molecules.

Give the catalyst and temperature used in the industrial process to convert long-chain molecules into shorter-chain molecules.

When C₁₃H₂₈ is used in this process, three different molecules are formed.

Complete the equation for this reaction.

This question is about gases.

The box gives the names of some gases.

Use gases from the box to answer these questions.

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

Name the most abundant gas in the Earth’s atmosphere.

Name the gas that is a compound.

Name the least reactive of the gases.

Name the gas formed by the complete combustion of hydrocarbons.

Describe the test for hydrogen gas.

This question is about octane (C₈H₁₈) which is produced in the gasoline fraction during fractional distillation of crude oil.

The diagram shows a fractionating column.

Describe how crude oil is separated into fractions in the fractionating column.

Octane can also be produced by the process of cracking.

Give the conditions for cracking.

A car is driven at constant speed for 4.00 km.

The exhaust gases are collected and their volume at room temperature and pressure (rtp) is 5.02 × 10⁵cm³.

The exhaust gases include carbon dioxide and oxides of nitrogen.

The carbon dioxide is removed from the exhaust gases. The volume of the remaining gases at rtp is 2.96 × 10⁵cm³.

Explain how oxides of nitrogen form in a car engine.

Give a reason why oxides of nitrogen should not be released into the atmosphere.

Show that the car produces less than 100 g of carbon dioxide per km.

[molar volume of carbon dioxide at rtp = 24 000 cm³]

The organic compound butadiene is a colourless gas used in the manufacture of synthetic rubber for tyres.

The displayed formula of butadiene is

Explain why butadiene is described as an unsaturated hydrocarbon.

Butadiene reacts with bromine water.

State the colour change that occurs during this reaction.

The equation for the reaction between butadiene and bromine can be shown using displayed formulae.

Br Br Br Br

The table gives some bond energies.

Use this information to calculate the enthalpy change, Δ H, for the reaction.

Include a sign in your answer.

ΔH =_........ kJ/mol

A scientist does an investigation to find out if butadiene would be a good fuel.

He burns a sample of butadiene gas and observes that carbon forms as black soot.

Complete the equation to explain the scientist’s observation.

Explain how one of the products, other than carbon, may cause a problem.

The equation for the combustion of butadiene in excess oxygen is

The enthalpy change for this reaction, Δ H, is – 3446 kJ/mol.

Complete the energy profile diagram for the reaction.

Label the enthalpy change for this reaction, Δ H, and the activation energy.

This question is about gases in the atmosphere.

The box gives the names of some gases in the atmosphere.

Choose gases from the box to answer these questions.

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

Identify a noble gas.

Identify a gas that makes up about 78% of the atmosphere.

Identify a greenhouse gas.

Identify a gas produced by the thermal decomposition of calcium carbonate.

Sulfur reacts with oxygen to produce sulfur dioxide gas.

Write a chemical equation for this reaction.

State an environmental problem caused when sulfur dioxide gas dissolves in water in the atmosphere.

A student uses this apparatus to investigate the heat energy released when a liquid fuel is burned.

This is the student’s method.

● measure the mass of the spirit burner and fuel

● add 100 cm³ of water to the copper can

● record the temperature of the water

● use the spirit burner to heat the water until the temperature rises by 30 °C

● immediately measure the new mass of the spirit burner and fuel

Suggest why the student measures the mass of the spirit burner and fuel immediately after heating the water.

When the fuel is burned, the student notices that a black solid forms on the bottom of the copper can.

Identify the black solid.

Explain why the black solid forms.

Show that the heat energy change, Q, to raise the temperature of 100 cm³ of water by 30 °C is approximately 13 kJ.

[c for water = 4.2 J/g/ °C]

The student burns 0.96 g of methanol, CH₃OH

Calculate the molar enthalpy change, Δ H, in kJ/mol, for the combustion of methanol.

Include a sign in your answer.

[M_r of methanol = 32]

ΔH =_........ kJ/mol

The table shows data book values for the molar enthalpy change, Δ H, for the combustion of some alcohols with different numbers of carbon atoms per molecule.

Plot the data values from the table on the grid.

Draw a straight line of best fit.

Number of carbon atoms

Deduce the value of Δ H for an alcohol with six carbon atoms per molecule.

Show on the graph how you obtained your answer.

State the relationship between Δ H and the number of carbon atoms per molecule.

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.

Ethanol, C₂H₅OH, can be manufactured from ethene and steam using a phosphoric acid catalyst.

State the temperature and pressure used in this manufacturing process.

Draw the displayed formula of ethanol.

Ethanol burns in a plentiful supply of air to form carbon dioxide and water.

Give the chemical equation for this reaction.

When the air supply is limited, incomplete combustion occurs and carbon monoxide forms.

State why carbon monoxide is poisonous to humans.

When ethanol reacts with ethanoic acid, an ester forms.

Give the name of this ester.

Butanedioic acid and ethanediol react together to form a polyester and water.

Give the name of this type of polymerisation.

Complete the equation.

Show only one repeat unit of the polyester.

O O

Crude oil is an important source of organic compounds.

The diagram shows crude oil being separated into different fractions.

Name the process used to separate crude oil into different fractions.

State what happens to the crude oil at X.

Describe the differences between fraction B and fraction E.

In your answer, refer to

● size of the molecules

● boiling point

● colour

● viscosity

Crude oil often contains sulfur as an impurity.

Explain why this is a problem when using crude oil fractions as fuels.

Dinitrogen tetraoxide, N₂O₄, is a colourless gas.

Nitrogen dioxide, NO₂, is a brown gas.

The two gases can exist together in dynamic equilibrium according to the equation

Explain what is meant by the term dynamic equilibrium.

Some N₂O₄ and some NO₂ are put into a sealed gas syringe and allowed to form an equilibrium mixture.

This equilibrium mixture is brown.

The pressure of the gas in the syringe is increased by pushing in the piston. The mixture is then allowed to reach a new equilibrium at the same temperature as before.

Explain why the new equilibrium mixture contains less NO₂ than the original equilibrium mixture.

A student suggests that the new equilibrium mixture would be lighter in colour than the original equilibrium mixture, as there is now less NO₂ present.

Suggest why the new equilibrium mixture is actually darker than the original.

Carbon monoxide, CO, and oxides of nitrogen are produced in a car engine when petrol is burned.

These oxides can be partly removed by using a catalytic converter fitted to the car’s exhaust system.

State how oxides of nitrogen are produced in the car engine.

Give a disadvantage of allowing oxides of nitrogen to escape into the atmosphere.

Write a chemical equation for the reaction between nitrogen monoxide, NO, and carbon monoxide to form carbon dioxide and nitrogen.