Organic ChemistryOxford AQA IGCSE Chemistry: Topic test

20 questions, 54 marks

Oxford AQA IGCSE Chemistry

Organic Chemistry topic test

Total 54 marks

Name

Class

Date

1
A camping equipment company sells gas canisters filled with either butane or propane for use in portable stoves. Butane has a higher boiling point than propane, so butane canisters do not vaporise fuel efficiently in cold winter conditions, while propane canisters continue to work well even in low temperatures.
(a)
Butane, C4H10, and propane, C3H8, are both saturated hydrocarbons. Which statement correctly explains why butane has a higher boiling point than propane?
[1 mark]
AButane has a longer carbon chain than propane, so it has stronger intermolecular forces between its molecules
BButane has a shorter carbon chain than propane, so its molecules are held together more weakly
CButane contains a carbon-carbon double bond, unlike propane
DButane molecules are ionic, so they attract each other more strongly than propane molecules
(b)
Which property, other than boiling point, would also be expected to differ between butane and propane because of their different chain lengths?
[1 mark]
Athe number of hydrogen atoms per carbon atom, since larger molecules have relatively more hydrogen per carbon
Btheir viscosity, since larger hydrocarbon molecules tend to be more viscous
Ctheir colour, since larger hydrocarbon molecules absorb more visible light
Dtheir reactivity with bromine water, since larger alkane molecules react readily with bromine water
(c)
State the general formula for alkanes, and use it to predict the molecular formula of pentane, the next member of the homologous series after butane.
[2 marks]
Total for question 1: 4 marks
2
A mechanic uses an exhaust gas analyser to test a family car's engine, which burns petrol, a hydrocarbon fuel. The analyser detects a higher-than-normal level of carbon monoxide in the exhaust gases, suggesting a fault with the engine's air supply.
(a)
What does the detection of carbon monoxide suggest about how the fuel is burning in this engine?
[1 mark]
AThe fuel is burning completely, with excess oxygen present
BThe fuel does not contain any carbon
CThe fuel is undergoing incomplete combustion due to a limited supply of oxygen
DThe fuel is reacting with nitrogen in the air rather than oxygen
(b)
Why is carbon monoxide considered dangerous to the car's occupants if it leaks into the cabin, compared with carbon dioxide?
[1 mark]
ACarbon monoxide reacts with the metal of the car body and weakens it
BCarbon monoxide has a strong smell that damages the lungs
CCarbon monoxide is more flammable than carbon dioxide
DCarbon monoxide is toxic, as it binds to haemoglobin in the blood and reduces the blood's ability to carry oxygen
(c)
Suggest what the mechanic should recommend to fix the fault suggested by this result, and explain why this would reduce the carbon monoxide produced.
[2 marks]
Total for question 2: 4 marks
3
A quality-control chemist at a chemical plant receives an unlabelled cylinder of hydrocarbon gas that should contain either ethene or ethane. To identify the gas, the chemist bubbles a sample through orange bromine water in a test tube, and separately checks the structural formulae of the two hydrocarbons against the plant's records.
(a)
Describe what the chemist should observe if the gas is ethene, and explain why this test works.
[3 marks]
(b)
Describe the structural formula of ethane and of ethene in words, stating how many hydrogen atoms are bonded to each carbon atom in each molecule, and use this to explain why ethene is described as 'unsaturated' while ethane is 'saturated'.
[4 marks]
Total for question 3: 7 marks
4
A cutlery manufacturer currently makes single-use forks and spoons from poly(propene), made by polymerising propene monomer. Environmental campaigners are pressuring the company to switch to a cornstarch-based biodegradable plastic instead, and the company is evaluating both options before deciding.
(a)
Explain how poly(propene) is manufactured from propene monomer, including why the type of polymerisation involved requires a particular feature in the monomer, and represent the polymerisation reaction in words (without drawing structures).
[6 marks]
(b)
Evaluate whether switching from poly(propene) to a cornstarch-based biodegradable plastic would solve the environmental problems associated with the company's single-use cutlery.
[6 marks]
Total for question 4: 12 marks
5
A road construction company needs a supply of bitumen, one of the products obtained when crude oil is separated into fractions by fractional distillation at a refinery. The company's site manager wants to understand why bitumen only becomes available once crude oil has been processed in this way.
(a)
Which statement best describes crude oil, before it is processed at the refinery?
[1 mark]
AA single pure hydrocarbon compound
BA mixture of a very large number of different compounds, most of which are hydrocarbons
CA pure compound made only of hydrogen atoms
DA mixture of metal ores and hydrocarbons in equal proportions
(b)
Which process is used to separate crude oil into fractions such as bitumen at the refinery?
[1 mark]
AFiltration
BElectrolysis
CNeutralisation
DFractional distillation, based on differences in boiling point
(c)
Explain why bitumen collects near the bottom of the fractionating column, rather than near the top, during fractional distillation.
[2 marks]
Total for question 5: 4 marks
6
A rural community with abundant sugar cane crops is considering building a small ethanol production plant, fermenting surplus sugar cane juice to produce ethanol fuel for local vehicles, instead of continuing to import petrol from overseas.
(a)
Which equation correctly represents the fermentation reaction used to produce this ethanol?
[1 mark]
AC6H12O6 → 2C2H5OH + 2CO2
BC2H4 + H2O → C2H5OH
CC2H5OH + O2 → CO2 + H2O
DC6H12O6 + O2 → C2H5OH + CO2
(b)
Which statement gives a genuine advantage of producing ethanol by fermentation for this community, compared with importing petrol?
[1 mark]
AFermentation requires very high pressure and expensive equipment
BFermentation produces no carbon dioxide at all
CSugar cane is a renewable resource that can be grown locally each year, unlike crude oil, which is non-renewable
DEthanol produced by fermentation cannot be used in vehicle engines
(c)
Suggest one disadvantage the community should consider before building the ethanol plant, relating to the land used to grow sugar cane.
[2 marks]
Total for question 6: 4 marks
7
A petrochemical plant cracks long-chain hydrocarbon fractions obtained from crude oil to produce ethene gas, which is later polymerised to make poly(ethene) for plastic bottles.
(a)
Describe the process of cracking used to produce ethene from long-chain hydrocarbon fractions in this plant, including the conditions used.
[3 marks]
(b)
After cracking, the plant needs to confirm that the gas collected is ethene rather than a saturated alkane by-product, before sending it for polymerisation. Describe a test the plant chemists could carry out and the result they would expect for ethene, and explain why removing any saturated alkane from the mixture matters before polymerisation.
[4 marks]
Total for question 7: 7 marks
8
A small-scale cider producer ferments apple juice to produce a batch of ethanol-based cider. Part of an open, exposed batch is accidentally left in contact with air for several weeks and turns sour, and a food scientist investigates what has happened and whether the sour batch could still be put to use.
(a)
Explain what has happened chemically to the exposed batch of cider to make it taste sour, and describe how the food scientist could show this using a simple property of the substance now present, compared with the property of the original ethanol.
[6 marks]
(b)
The food scientist suggests using the sour batch, together with some of the original ethanol-based cider, to produce a fruity-smelling ester as a new flavouring ingredient. Describe how this ester could be made, name the ester produced, and explain why this product would be suitable as a flavouring.
[6 marks]
Total for question 8: 12 marks

End of questions