Alkenes

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.

This question is about alkanes and alkenes.

Ethane and ethene each react with bromine, but under different conditions.

Give a reason why ethane does not undergo an addition reaction with bromine.

Complete the equation for the substitution reaction between ethane and bromine, including an essential condition for the reaction.

condition

Give the colour change that occurs when ethene reacts with bromine water.

The diagram shows the displayed formulae of two compounds in the homologous series of alkenes.

Compounds in the same homologous series have the same general formula.

Give two other characteristics of compounds in the same homologous series.

Explain why the alkenes in the diagram are isomers.

Draw the displayed formula of another alkene that is an isomer of these two alkenes.

The reaction used to make poly(ethene) can be represented by this equation.

H H n

Describe the differences between the reactant and the product in this reaction.

Refer to carbon chain length, type of bond and state of matter in your answer.

This question is about crude oil.

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

Some of the long-chain alkanes obtained from fractional distillation are cracked, producing shorter-chain alkanes and ethene.

Give the conditions necessary for cracking to occur.

Explain why shorter-chain alkanes are more useful than longer-chain alkanes.

Ethene reacts with bromine.

The equation shows the displayed formulae of the reactants and product.

H H

Br Br

The table shows some bond energies.

Show that the molar enthalpy change, Δ H, for this reaction is about –100 kJ/mol.

ΔH =_........ kJ/mol

Explain why the reaction between ethene and bromine is exothermic.

Refer to bond energies in your answer.

Crude oil is an important source of organic compounds.

The diagram shows how crude oil can be separated into useful mixtures of hydrocarbons.

Give the name of this method of separation.

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

Give the letter of the mixture that is most likely to contain a hydrocarbon with six carbon atoms.

Give the name of mixture D.

Give a use for mixture B.

Explain, in terms of intermolecular forces, why a hydrocarbon in mixture B has a higher boiling point than a hydrocarbon in mixture D.

Catalytic cracking can be used to break down long‑chain hydrocarbons to produce shorter‑chain alkanes and alkenes.

Give the name of a catalyst used in catalytic cracking.

Complete the equation to show two different alkenes that could be produced in this cracking reaction.

Give one important use for short‑chain alkenes.

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.

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.

A teacher uses this apparatus to test the products of the combustion of liquid hydrocarbons.

Explain the change in appearance that occurs in the limewater.

The equation represents the complete combustion of an alkene.

C_nH_2n + oxygen carbon dioxide + nH₂O

Complete combustion of 0.0100 mol of the alkene produces 2.16 g of water.

Determine the molecular formula of this alkene.

[for H₂O, M_r = 18]

Give a reason why the mass of pure water that collects in the U-tube is less than 2.16 g.

Give a physical test to show that the water that collects in the U-tube is pure.

The teacher burns 30.0 g of heptane.

This is the equation for the complete combustion of heptane.

Calculate the minimum mass of oxygen needed for the complete combustion of 30.0 g of heptane.

[for C₇H₁₆, M_r = 100 for O₂, M_r = 32]

The table gives some information about the halogens, fluorine, chlorine, bromine and iodine.

Complete the table by giving the missing information.

Describe a test to show that a colourless liquid is an alkene.

A student is given an aqueous solution of chlorine and an aqueous solution of sodium iodide.

The student mixes the two solutions.

Explain the colour change that occurs.

Fractional distillation is used to separate crude oil into fractions.

The diagram shows a fractionating column and the fractions obtained from crude oil.

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

Give a use for kerosene and a use for bitumen.

kerosene

bitumen

Some fractions obtained from crude oil are cracked to form alkenes.

Describe what is meant by cracking.

Ethene is obtained by cracking.

This is the displayed formula of ethene.

Explain why ethene is described as an unsaturated hydrocarbon.

Describe a test to show that ethene is unsaturated.

This question is about alkanes and alkenes.

The alkane C₅H₁₂ has three isomers.

State what is meant by the term isomers.

Calculate the relative formula mass (M_r) of C₅H₁₂

This is the displayed formula of one of the isomers.

H H H H H

Give the name of this isomer.

Draw the displayed formulae of the other two isomers.

Isomer 1
Isomer 2

Ethane (C₂H₆) and ethene (C₂H₄) both react with bromine.

Describe the differences in the reactions of ethane and ethene with bromine.

Refer to the conditions, the products and the types of reaction involved.

This question is about the unsaturated hydrocarbon, ethene.

The displayed formula of ethene is

State the meaning of the term hydrocarbon.

Give the reason why ethene is described as unsaturated.

Ethene is bubbled through bromine water until there is no further colour change.

Which of these is the appearance of the solution formed?

Ethanol is produced industrially by the reaction between ethene and steam.

The equation for the reaction is

State the temperature and pressure used in this reaction.

temperature

pressure

Give the molecular formula of ethanol.

Organic compounds can exist as isomers.

Explain what is meant by the term isomers.

Organic compound Q reacts with bromine, without the presence of ultraviolet radiation, to form the compound C₄H₈Br₂

Draw the displayed formulae of two isomers of Q.

An acrylic polymer can be formed from molecules with this structure.

A student describes the molecule as an unsaturated hydrocarbon.

Explain whether this is a correct description.

Name the type of polymerisation that occurs in the formation of the polymer.

Complete the equation for the polymerisation reaction.

Octane is a compound in petrol.

The equation for the complete combustion of octane is

The fuel tank of a car contains 50.0 dm³ of octane.

Calculate the mass, in kg, of carbon dioxide formed if all the octane in the fuel tank undergoes complete combustion.

[mass of 1 dm³ of octane = 700 g]

State an environmental problem caused by carbon dioxide.

This question is about alkenes and alkanes.

Complete the table by giving the missing information about the alkene with the molecular formula C₃H₆

Alkenes are unsaturated compounds.

State what is meant by the term unsaturated.

Describe a test to show that a compound is unsaturated.

When the alkane methane reacts with chlorine, the products are chloromethane (CH₃Cl) and hydrogen chloride gas.

Give a chemical equation for this reaction.

What is the name of this type of reaction?

State the condition needed for this reaction to occur.

When ethane reacts with chlorine, one of the products of the reaction has the formula C₂H₄Cl₂

There are two isomers with this formula.

State what is meant by the term isomers.

Draw the displayed formulae of the two isomers with the formula C₂H₄Cl₂

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.

The Group 7 elements are called halogens.

Halogens form compounds called halides.

Three of the halogens are represented by the formulae X₂, Y₂ and Z₂

Solutions of these halogens are added separately to solutions of sodium halides, NaX, NaY and NaZ.

The table shows whether or not a reaction occurs.

Use the information in the table to deduce the order of reactivity of the halogens X₂, Y₂ and Z₂

An aqueous solution of halogen Y₂ is orange.

This solution is decolourised when it reacts with an alkene.

Deduce the identity of halogen Y₂

The table shows some physical properties of the halogens.

Complete the table by predicting a boiling point for chlorine, the state of fluorine at room temperature and the colour of astatine.

Why do the halogens have similar chemical properties?

A teacher uses this apparatus to demonstrate the reaction between chlorine gas and iron wool. The teacher does the reaction in a fume cupboard.

Suggest why the teacher does the reaction in a fume cupboard.

The product of the reaction between iron and chlorine is iron(III) chloride.

The ions in iron(III) chloride are Fe³⁺ and Cl⁻

Use this information to give the chemical equation for this reaction.

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.