Alkanes (Edexcel IGCSE Science (Double Award) (Modular): Chemistry Unit 1): Exam Questions

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

i) Explain which homologous series compound B belongs to.

[2]

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

[1]

iii) 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.

[3]

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.

i) State the type of polymer formed from compound C.

[1]

ii) Name the polymer formed from compound C.

[1]

iii) Draw the structure of this polymer.

Include the displayed formula of the repeat unit.

[2]

This question is about alkanes and alkenes.

i) Complete the boxes by giving the missing information about the alkane with the molecular formula C₂H₆

[3]

ii) Complete the chemical equation for the complete combustion of the alkane C₂H₆

[1]

...........C₂H₆ + ...........O₂ → ...........CO₂ + ...........H₂O

iii) Incomplete combustion occurs when the air supply is limited.

Give the names of two products of incomplete combustion.

[2]

i) Draw displayed formulae for two different alkenes with the molecular formula C₄H₈

[2]

ii) State the term used for compounds with the same molecular formula but different structural formulae.

[1]

An alkene with molecular formula C₄H₈ reacts with bromine to form a compound with molecular formula C₄H₈Br₂

What is the name of this type of reaction?

The alkene C₃H₆ can be polymerised to form the polymer poly(propene).

i) Complete the equation for this polymerisation reaction.

[2]

ii) Two ways of disposing of polymers such as poly(propene) are:

• burying them in landfill sites

• burning them to release heat energy

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

[3]

Ethane and bromine can react in the following reaction:

What name is given to this type of reaction?

Methane and bromine react to form bromomethane and hydrogen bromide. 

What does this reaction occur in the presence of? 

Alkanes are hydrocarbons. The structure of a molecule of butane is shown.

Which of the following is the empirical formula for butane?

The graph below shows the boiling points of some alkanes plotted against the number of carbon atoms in one molecule of each alkane.

A molecule of pentane contains five carbon atoms. Use the graph to estimate the boiling point of pentane.

boiling point of pentane = .............................................................. °C

When pentane reacts with bromine in the presence of ultraviolet radiation, bromopentane is produced.

i) State the name of the other product formed in this reaction.

[1]

ii) Give the molecular formula of bromopentane.

[1]

Draw the displayed formula of the three isomers of bromopentane.

This question is about alkanes and alkenes.

The alkane, C₄H₁₀, has two isomers.

i) Calculate the relative formula mass (M_r) of C₄H₁₀.

M_r of C₄H₁₀ = ..............................................................

[1]

ii) Explain the meaning of the term isomers.

[2]

iii) This is the displayed formula of one of the isomers:

State the name of this isomer.

[1]

iv) Draw the displayed formula of the other isomer.

[1]

Bromine will react with C₄H₁₀ and C₄H₈.

Explain the difference in the reactions of each substance with bromine.

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

There are three isomers with the molecular formula C₅H₁₂

One of these isomers is pentane.

The displayed formula for pentane is

i) State what is meant by the term isomers.

[2]

ii) Draw the displayed formula for another isomer of C₅H₁₂

[2]

Pentane reacts with bromine in the presence of ultraviolet radiation.

i) Complete the equation for this reaction.

[2]

C₅H₁₂ + Br₂ → .................... + ....................

ii) Give the name of this type of reaction.

[1]

Hexane and cyclohexane are both hydrocarbons containing six carbon atoms. Their structures are shown below.

Compare the structures of hexane and cyclohexane.

A sample of one of these structures was found to contain 83.72% carbon.

i) Calculate its empirical formula.

Show your working.

[3]

ii) Deduce whether the sample was hexane or cyclohexane.

[1]

i) Give the molecular formula of cyclohexane.

[1]

ii) Draw the displayed formula of an isomer of cyclohexane.

[1]

In the presence of ultraviolet radiation, hexane will react with chlorine to form hydrogen chloride and another compound, X. Compound X will undergo a further substitution reaction when heated with sodium hydroxide solution to form sodium chloride and a compound with the formula CH₃(CH₂)₅OH.

Cyclohexane will also react with chlorine in the presence of ultraviolet radiation to form hydrogen chloride and compound Y. When heated with sodium hydroxide solution, compound Y will undergo a further substitution reaction to form sodium chloride and another product, Z. Give the names of compounds X, Y and Z.

Three consecutive straight-chain members of the same homologous series are pentane, hexane and heptane.

Pentane is the compound containing the least number of carbon atoms.

Suggest the molecular formula of heptane.

Draw one line from each alkane to its boiling point.

Alkynes are hydrocarbons with the general formula C_nH_2n-2. The alkyne containing 2 carbon atoms is ethyne, C₂H₂. 

State, with a reason, whether the boiling point of ethyne would be expected to be higher or lower than the boiling point of ethane, C₂H₆.

Complete the dot-and-cross diagram for a molecule of ethyne, C₂H₂.