11 mark
Which of these formulae is that of an alkane?
| ☐ | A | C6H11 | |
| ☐ | B | C8H16 | |
| ☐ | C | C10H22 | |
| ☐ | D | C12H28 |
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Alkanes (Edexcel IGCSE Chemistry)
Topic Questions
21 mark
The table shows the displayed formulae of some organic compounds.
Which two are not classed as alkanes?
| ☐ | A | R and S | |
| ☐ | B | S and T | |
| ☐ | C | P and Q | |
| ☐ | D | R and T |
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31 mark
What is the correct chemical formula of butane?
| ☐ | A | C3H6 | |
| ☐ | B | C3H8 | |
| ☐ | C | C4H8 | |
| ☐ | D | C4H10 |
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4a2 marks
The structure of a molecule of propane is shown as
Give the names of the elements combined together in propane.
4b3 marks
Propane can burn completely in oxygen to form carbon dioxide and water.
i)
Write the word equation for this reaction.
(2)
ii)
Propane is a fuel.
Give the reason why fuels are burned.
Give the reason why fuels are burned.
(1)
4c1 mark
Which product is formed when there is incomplete combustion of propane?
| ☐ | A | sulfur dioxide | |
| ☐ | B | oxygen | |
| ☐ | C | hydrogen | |
| ☐ | D | carbon monoxide |
4d1 mark
Which of the following is the formula of an alkane?
| ☐ | A | C6H5OH | |
| ☐ | B | CH3CH2CH2CH3 | |
| ☐ | C | H2C=CHCH2CH3 | |
| ☐ | D | C6H12 |
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5a2 marks
This question is about alkanes.
Draw one line from the name of the alkane to the correct displayed formula.
5b1 mark
What is the general formula of alkanes?
Tick (✓) one box.
| CnH2n | |
| CnH2n+1 | |
| CnH2n+2 |
5c1 mark
What type of bond is formed between the carbon and hydrogen atoms in an alkane?
5d3 marks
Ethane can react with chlorine in a substitution reaction where one of the hydrogen atoms in ethane is replaced by a chlorine atom.
i)
Complete the equation for the reaction
ethane + ......................... → ........................................... + hydrogen chloride
(2)
ii)
What condition is necessary for this reaction to occur?
(1)
| ☐ | A | a catalyst | |
| ☐ | B | 30 °C and no oxygen | |
| ☐ | C | ultraviolet radiaton | |
| ☐ | D | none - it will occur at room temperature and pressure |
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1a4 marks
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)
1b3 marks
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)
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2a
4 marks
4 marksSeparate: Chemistry Only
The alkanes are generally unreactive. Their reactions include combustion and substitution.
The complete combustion of an alkane gives carbon dioxide and water.
i)
10 cm3 of butane is mixed with 100 cm3 of oxygen, which is an excess. The mixture is ignited. What is the volume of unreacted oxygen left and what is the volume of carbon dioxide formed?
C4H10 (g) + 6.5O2 (g) → 4CO2 (g) + 5H2O (l)
Volume of oxygen left = .................................................. cm3
Volume of carbon dioxide formed = .................................................. cm3
(2)
ii)
Why is the incomplete combustion of any alkane dangerous, particularly in an enclosed space?
(2)
2b5 marks
Many organic compounds which contain a halogen have chloro, bromo or iodo in their name.
The following diagram shows the structure of 1-chloropropane.
i)
Draw the structure of an isomer of this compound.
(1)
ii)
Describe how 1-chloropropane could be made from propane.
(2)
iii)
Suggest an explanation why the method you have described in (ii) does not produce a pure sample of 1-chloropropane.
(2)
2c3 marks
Separate: Chemistry Only
Organic halides react with water to form an alcohol and a halide ion.
CH3–CH2–I + H2O → CH3–CH2–OH + I–
i)
Describe how you could show that the reaction mixture contained an iodide ion.
(2)
ii)
Name the alcohol formed when 1-chloropropane reacts with water.
(1)
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3a4 marks
An alkane containing six carbon atoms can exist as a number of different structures. Two of these structures are shown below.
Compare the structures of hexane and cyclohexane.
3b4 marks
4 marksA sample of one of these structures was found to contain 83.72% carbon.
i)
Calculate its empirical formula.
Show your working.
(3)
ii)
Dedeuce whether the sample was hexane or cyclohexane.
(1)
3c2 marks
i)
Give the molecular formula of cyclohexane.
(1)
ii)
Draw the displayed formula of an isomer of cyclohexane.
(1)
3d3 marks
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 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.
| Compound X | ....................................................................................... |
| Compound Y | ....................................................................................... |
| Compound Z | ....................................................................................... |
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4a1 mark
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.
4b3 marks
Draw one line from each alkane to its boiling point.
4c2 marks
Alkynes are hydrocarbons with the general formula CnH2n-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.
4d2 marks
Complete the dot-and-cross diagram for a molecule of ethyne, C2H2.
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5a2 marks
This question is about the reactions of the gas ethane, C2H6.
Write the equation which represents the complete combustion of 1 mole of ethane.
5b2 marks
Ethane will react with chlorine in the presence of ultraviolet radiation to form chloroethane and hydrogen chloride.
C2H6 (g) + Cl2 (g) → C2H5Cl (g) + HCl (g)
Rewrite this equation to show the displayed formulae of the reactants and products.
5c3 marks
3 marksSeparate: Chemistry Only
The enthalpy change of this reaction is -122 kJ/mol.
Use the bond energy data in the table below to calculate the bond energy of the C-Cl bond.
| Bond | Bond energy (kJ/mol) |
| C – H | 413 |
| C – C | 347 |
| H – Cl | 432 |
| Cl – Cl | 243 |
bond energy ........................................................ kJ / mol
5d2 marks
Separate: Chemistry Only
Use your answer from part c) to suggest which compound, ethane or chloroethane, is the more reactive.
Explain your answer.
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1a6 marks
The table shows the molecular formulae of six organic compounds, A, B, C, D, E and F.
| A | B | C | D | E | F |
| C2H4 | C2H6 | C3H6 | C3H8 | C4H8 | C4H10 |
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)
1b4 marks
Describe how compound D can be obtained from crude oil using the industrial process of fractional distillation.
1c4 marks
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)
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2a6 marks
This question is about alkanes and alkenes.
i)
Complete the boxes by giving the missing information about the alkane with the molecular formula C2H6
| molecular formula | C2H6 |
| name | |
| empirical formula | |
| displayed formula |
(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)
2b4 marks
An alkene with molecular formula C4H8 reacts with bromine to form a compound with molecular formula C4H8Br2
i)
What is the name of this type of reaction?
(1)
| ☐ | A | addition | |
| ☐ | B | decomposition | |
| ☐ | C | precipitation | |
| ☐ | D | substitution |
ii)
Draw displayed formulae for two different alkenes with the molecular formula C4H8
(2)
|
|
iii)
State the term used for compounds with the same molecular formula but different structural formulae.
(1)
2c5 marks
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)
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31 mark
Ethane and bromine can react in the following reaction:
What name is given to this type of reaction?
| ☐ | A | Substitution | |
| ☐ | B | Addition | |
| ☐ | C | Dehydration | |
| ☐ | D | Thermal decomposition |
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41 mark
Methane and bromine react to form bromomethane and hydrogen bromide.
What does this reaction occur in the presence of?
| ☐ | A | Infrared radiation | |
| ☐ | B | Visible light | |
| ☐ | C | Untraviolet radiation | |
| ☐ | D | Ozone |
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5a1 mark
Alkanes are hydrocarbons.
The structure of a molecule of butane is shown.
Which of the following is the empirical formula for butane?
| ☐ | A | CH | |
| ☐ | B | CH2 | |
| ☐ | C | C2H5 | |
| ☐ | D | C4H10 |
5b1 mark
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
5c2 marks
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)
5d3 marks
Draw the displayed formula of the three isomers of bromopentane.
| isomer 1 | isomer 2 | isomer 3 |
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