Organic ChemistryAQA GCSE Chemistry: Topic test

20 questions, 54 marks

AQA GCSE Chemistry

Organic Chemistry topic test

Total 54 marks

Name

Class

Date

1
An aviation fuel supplier is comparing different fractions obtained from crude oil by fractional distillation for use in aircraft. Kerosene (used as jet fuel) has a lower boiling point, is less viscous and flows more easily at the very low temperatures found at cruising altitude than heavier fractions such as diesel or heavy fuel oil, which are used in ships and large engines instead.
(a)
Kerosene consists mainly of hydrocarbon molecules with shorter carbon chains than heavy fuel oil. What effect does this shorter chain length have on kerosene's boiling point and viscosity compared with heavy fuel oil?
[1 mark]
ALower boiling point and lower viscosity
BHigher boiling point and higher viscosity
CLower boiling point and higher viscosity
DHigher boiling point and lower viscosity
(b)
Fractional distillation separates crude oil into fractions based mainly on which property of the hydrocarbon molecules?
[1 mark]
ATheir colour
BTheir boiling point
CTheir electrical charge
DTheir solubility in water
(c)
Explain why heavy fuel oil, rather than kerosene, is usually chosen to power large ships, referring to viscosity and flammability.
[2 marks]
Total for question 1: 4 marks
2
A gas safety inspector is investigating a poorly ventilated gas heater that burns methane (an alkane). With a good supply of air, methane burns completely to form carbon dioxide and water. The inspector finds that, in this heater, there is not enough oxygen reaching the flame.
(a)
Which of these is the correctly balanced equation for the complete combustion of methane?
[1 mark]
ACH4 + O2 -> CO2 + 2H2O
BCH4 + 2O2 -> CO + 2H2O
CCH4 + 2O2 -> CO2 + 2H2O
D2CH4 + O2 -> 2CO2 + 4H2O
(b)
Because there is not enough oxygen reaching the flame, the methane in this heater undergoes incomplete combustion instead. Which products would this produce?
[1 mark]
ACarbon dioxide and water only
BHydrogen gas and oxygen gas
CMethane is simply released unburned, with no products formed
DCarbon monoxide and/or carbon (soot) as well as water
(c)
Explain why the carbon monoxide produced by incomplete combustion in this heater is particularly dangerous to the people in the house.
[2 marks]
Total for question 2: 4 marks
3
A recycling company is developing a chemical recycling process for mixed plastic waste. Long-chain hydrocarbon molecules recovered from the waste plastic are heated strongly with a catalyst, breaking them down (cracking) into a mixture of shorter, more useful hydrocarbon molecules, including some alkenes, which can then be used to manufacture new plastics.
(a)
Describe the general conditions used to crack long-chain hydrocarbons, and state the general formula of the alkenes produced.
[3 marks]
(b)
The recycling company's chemist tests a sample of the cracked product mixture with bromine water. Describe and explain what she would observe if the mixture contains alkenes, and explain why this test would not give the same result with an unreacted long-chain alkane.
[4 marks]
Total for question 3: 7 marks
4
A small craft brewery is testing a new yeast strain. Sugar solution is fermented with the yeast at a controlled temperature to produce ethanol, and quality control also checks an open bottle of beer that was accidentally left out, uncapped, for a week, which has since developed a sour, vinegary taste.
(a)
Describe the conditions needed for fermentation to produce ethanol efficiently, and explain why the brewery controls the fermentation temperature carefully rather than using the highest possible temperature.
[6 marks]
(b)
Explain, in terms of the chemical reaction taking place, why the open bottle of beer has developed a sour, vinegary taste after a week, and describe one chemical test the quality control team could use to show that the sour liquid is now acidic rather than the original beer.
[6 marks]
Total for question 4: 12 marks
5
A candle manufacturer selects paraffin wax, a solid mixture of long-chain hydrocarbons obtained from crude oil, for making candles, and compares it with a lighter, more volatile liquid fraction sometimes used as lamp oil. At room temperature, paraffin wax is solid while lamp oil is a free-flowing liquid.
(a)
What does the difference in physical state between solid paraffin wax and liquid lamp oil at room temperature mainly tell you about their hydrocarbon molecules?
[1 mark]
AParaffin wax molecules are longer-chain hydrocarbons than lamp oil, so it has a higher melting point
BParaffin wax molecules are shorter-chain hydrocarbons than lamp oil
CParaffin wax and lamp oil have identical chain lengths
DParaffin wax contains no carbon atoms
(b)
The manufacturer also notes that lamp oil is more flammable and easier to ignite than paraffin wax at room temperature. What is the best explanation for this?
[1 mark]
ALamp oil contains oxygen atoms, unlike paraffin wax
BLamp oil has a lower boiling point/is more volatile, so it produces flammable vapour more easily at room temperature
CParaffin wax is a different element to lamp oil
DLamp oil is a stronger acid than paraffin wax
(c)
Explain why the manufacturer would need to melt the solid paraffin wax before it can be poured into a candle mould, in terms of the intermolecular forces between its hydrocarbon molecules.
[2 marks]
Total for question 5: 4 marks
6
A cleaning products company is choosing an alkane solvent for a new surface cleaner, from a range including pentane (C5H12), hexane (C6H14), heptane (C7H16) and octane (C8H18). They want the solvent to evaporate at a controlled, moderate rate once applied to a surface, not too quickly and not too slowly.
(a)
Which general formula correctly represents the homologous series of alkanes that these four solvents belong to?
[1 mark]
ACnH2n
BCnHn
CCnH2n+2
DCnH2n-2
(b)
As the carbon chain length increases from pentane to octane, what happens to the boiling point of the alkanes, and why?
[1 mark]
ABoiling point decreases, because larger molecules have weaker intermolecular forces
BBoiling point stays the same, because all alkanes have identical intermolecular forces
CBoiling point increases, because covalent bonds within the molecules become stronger
DBoiling point increases, because larger molecules have stronger intermolecular forces
(c)
The company chooses hexane, which has a moderate boiling point among the four options. Explain why a solvent with too high a boiling point would be unsuitable for a surface cleaner intended to evaporate after use.
[2 marks]
Total for question 6: 4 marks
7
A chemical company uses propene (C3H6), obtained by cracking, as the starting material for three different addition reactions: reacting it with hydrogen to make propane, reacting it with steam (water) to make propan-1-ol, and reacting it with bromine to make 1,2-dibromopropane.
(a)
Explain, in terms of the carbon-carbon double bond, why propene can undergo these three addition reactions but propane cannot.
[3 marks]
(b)
State the conditions needed for propene to react with hydrogen to form propane, and describe how you would use bromine water to show that a sample of gas is propene rather than propane.
[4 marks]
Total for question 7: 7 marks
8
A biomedical materials company is developing a biodegradable surgical suture made from a synthetic polyester, formed by condensation polymerisation of two different monomers. Researchers compare its structure with the natural protein collagen, also formed by condensation polymerisation, which is found in human tissue.
(a)
Describe condensation polymerisation, using the manufacture of the polyester suture as an example, and explain one way condensation polymerisation differs from the addition polymerisation used to make everyday plastics such as poly(ethene).
[6 marks]
(b)
Explain how the natural protein collagen is also formed by condensation polymerisation, and describe the key structural similarity and one key difference between the synthetic polyester suture and the natural protein collagen.
[6 marks]
Total for question 8: 12 marks

End of questions