Exam code: 7405
A fraction of distilled crude oil contains molecules with between 15 and 19 carbon atoms. This fraction is cracked by strong heating.
Why is this fraction cracked?
| To produce alkenes | To produce smaller molecules which are in higher demand | To insert oxygen atoms into the hydrocarbons |
A | ✓ | ✓ | ✓ |
B | ✓ | ✓ |
|
C |
| ✓ | ✓ |
D | ✓ |
|
|
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The hydrocarbon C17H36 can be cracked.
Which compound is the least likely to be produced in this reaction?
C16H34
C8H16
C4H8
C3H8
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In the presence of ultraviolet light, ethane and chlorine react to give a mixture of products.
Which compound could be present in the mixture of products?
CH3CH2CH2CH2CH3
CH3CH2CH2CH3
CH3CH2CH2Cl
CH3Cl
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Which hydrocarbon would not be collected in the inverted tube by heating pentane, CH3(CH2)3CH3, in the apparatus shown?
CH3(CH2)8CH3
CH3CH2CH=CH2
CH3CH3
CH4
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Ultraviolet light initiates the following reaction.
alkane + chlorine → chloroalkane + hydrogen chloride
What happens to chlorine in this photochemical reaction?
heterolytic fission to give an electrophile
homolytic fission to give an electrophile
heterolytic fission to give a positive and negative ion
homolytic fission to give free radicals
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Which of the following products are possible from the incomplete combustion of alkanes?
| Carbon | Carbon monoxide | Hydrogen |
A | ✓ | ✓ |
|
B | ✓ |
| ✓ |
C |
| ✓ | ✓ |
D | ✓ | ✓ | ✓ |
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The combustion of fossil fuels results in the release of pollutant gases.
Which row correctly describes the environmental problems associated with the pollutant gases?
| Sulfur dioxide | Nitrogen oxides | Carbon particulates |
A | Acid rain | Global warming | Global warming |
B | Global warming | Acid rain | Global dimming |
C | Acid rain | Acid rain | Global dimming |
D | Global warming | Global dimming | Acid rain |
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Fractional distillation is used to separate the hydrocarbon mixture of crude oil by boiling point.
Which is the correct description of the fractional distillation process?
Fractional distillation is a physical process that breaks the hydrocarbon covalent bonds
Fractional distillation is a chemical process that breaks the hydrocarbon covalent bonds
Fractional distillation is a physical process that overcomes the intermolecular forces between hydrocarbon molecules
Fractional distillation is a chemical process that overcomes the intermolecular forces between hydrocarbon molecules
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Which equation is correct for the complete combustion of heptane?
2C7H16 + 22O2 → 14CO2 + 16H2O
2C7H16 + 15O2 → 14CO + 16H2O
2C7H14 + 21O2 → 14CO2 + 14H2O
2C6H14 + 19O2 → 12CO2 + 14H2O
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Ethane reacts with bromine in the presence of ultraviolet light to form bromoethane and hydrogen bromide.
C2H6 + Br2 → C2H5Br + HBr
Which equation represents the desired termination step for this reaction?
C2H5● + Br2 → C2H5Br + Br●
C2H5● + Br● → C2H5Br
Br2 → 2Br●
2C2H5● → C4H10
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Which equation represents a valid propagation step in the free radical reaction between ethane and bromine?
C2H6 + Br• → C2H5Br + H•
C2H5• + Br• → C2H5Br
C2H5Br + Br• → C2H4Br• + HBr
C2H5Br + H• → C2H5• + HBr
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Nitrogen oxide, NO, reacts with octane in the catalytic converter of a car to create non-toxic products.
Which equation correctly represents this reaction?
C8H18 + 17NO → 8CO + 8.5N2 + 9H2O
C8H18 + 25NO → 8CO2 + 12.5N2 + 9H2O
C8H16 + 16NO → 8CO + 8N2 + 8H2O
C8H16 + 24NO → 8CO2 + 12N2 + 8H2O
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Isooctane, shown below, can be added to fuels for improved performance.
Which is the correct equation for the complete combustion of isooctane?
C8H18 + 8½O2 → 8CO + 9H2O
C8H18 + 12½O2 → 8CO2 + 9H2O
C7H16 + 11O2 → 7CO2 + 8H2O
C8H18 + 13O2 → 8CO2 + 9H2O
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Sulfur dioxide, SO2, is a pollutant that can be produced during the combustion of impurities in hydrocarbon based fuels.
Which of the statements is correct?
Sulfur dioxide does not dissolve in water
Sulfur dioxide is responsible for global dimming
Sulfur dioxide is an acidic gas
Sulfur dioxide can be removed from flue gases by reacting them with magnesium carbonate
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Which of these organic compounds would undergo free radical substitution?
| ethane | fluoroethane | ethene | ethanal |
A | ✓ | ✓ | ✓ | ✓ |
B | ✓ | ✓ | ✓ |
|
C | ✓ | ✓ |
|
|
D | ✓ |
|
| ✓ |
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Which is the correct balanced symbol equation for the cracking of eicosane, C20H42?
C20H42 + 30½O2 → 20CO2 + 21H2O
C20H42 → C8H16 + C6H12 + 2C3H6
C20H42 → C8H16 + 2C5H10 + C2H6
C20H42 → C7H16 + C6H14 + C4H10 + C3H8
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Low demand, long chain hydrocarbons can be cracked into high demand, shorter chain hydrocarbons. This can be done by thermal or catalytic cracking.
Which of the statements about catalytic cracking is correct?
Catalytic cracking occurs at temperatures between 750 and 1200K
Catalytic cracking occurs in the presence of oxygen
Catalytic cracking occurs at pressures 7000 kPa
Catalytic cracking produces branched alkanes, cycloalkanes, aromatic compounds and alkenes
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Bitumen, diesel, liquified petroleum gases (LPG) and petrol are four of the fractions obtained by the fractional distillation of crude oil.
Which is the correct order of these fractions from lowest to highest boiling point?
Liquified petroleum gases (LPG), petrol, diesel, bitumen
Bitumen, diesel, liquified petroleum gases (LPG), petrol
Liquified petroleum gases (LPG), petrol, bitumen, diesel
Bitumen, diesel, petrol, liquified petroleum gases (LPG)
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Which of the following statements about the cracking of hydrocarbons is correct?
Thermal cracking occurs at high temperature, high pressure and in the presence of a zeolite catalyst
Catalytic cracking involves the formation of free radical intermediates
Thermal and catalytic cracking are used to convert low demand long chain hydrocarbons into high supply short chain hydrocarbons
Catalytic cracking is used to produce mainly motor fuels and aromatic hydrocarbons
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Which statement about crude oil fractional distillation is not correct?
The fractional distillation column has a negative temperature gradient
Each fraction contains a mixture of hydrocarbons
Gaseous fractions are formed by overcoming intermolecular forces
More volatile fractions are found at the bottom of the fractional distillation column
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Ethane reacts with chlorine by free radical substitution to produce a mixture of products.
Which is not a possible product of this reaction?
CH3CH2CH3
CH3CH2Cl
CH3CH2CH2CH3
HCl
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The petrol additive tetraethyl-lead(IV), Pb(C2H5)4, is now banned in many countries.
When it is completely burned in air, lead(II) oxide, CO2 and H2O are formed.
How many moles of oxygen are required to burn one mole of Pb(C2H5)4?
9.5
11
13.5
27
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Nitric oxide, NO, reacts with octane in the catalytic converter of a car to create three non-toxic products.
What are the whole number coefficients in the balanced equation for this reaction?
34 : 17
50 : 25
2 : 1
24 : 12
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The cracking of eicosane, C20H42, produces a hydrocarbon that is in very high demand for transportation and also three consecutive members of the same homologous series of hydrocarbons.
What are the correct products of cracking for the given reaction?
Butene, octane, pentene, propene
Butane, butene, hexene, octane
Ethane, hexene, heptene, pentene
Ethene, hexane, heptene, pentene
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Unburnt hydrocarbons from fuels can be oxidised to carbon dioxide and water in the catalytic converter of a car.
What is the correct coefficient to balance the oxidising agent, [O], in this reaction?
CnH2n+2 + _[O] → nCO2 + (n+1)H2O
n+2
2n+2
2n+1
3n+1
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Which statement about cracking is correct?
Thermal cracking occurs at high temperatures in the presence of zeolites to produce a high percentage of alkenes
Thermal cracking occurs at high temperatures and high pressures to mainly produce motor fuels and aromatic hydrocarbons
Catalytic cracking occurs at high temperatures in the presence of zeolites to mainly produce motor fuels and aromatic hydrocarbons
Catalytic cracking occurs at high temperatures and high pressures to produce a high percentage of alkenes
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Ethane reacts with bromine in the presence of ultraviolet light to form dibromoethane and hydrogen bromide.
The reaction proceeds via free radical substitution involving initiation, propagation and termination steps.
What is the minimum number of free radical mechanism steps to produce dibromoethane?
5
6
7
8
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Ethane reacts with chlorine in the presence of ultraviolet light to form trichloroethane and hydrogen chloride.
The reaction proceeds via free radical substitution involving initiation, propagation and termination steps.
Which propagation equation is involved in the free radical reaction to form trichloroethane?
C2H6 + Cl● → C2H6● + HCl
C2H3Cl2 + Cl● → C2H3Cl3 + H●
C2H5 + Cl2 → C2H5Cl + Cl●
C2H4Cl● + Cl2 → C2H4Cl2 + Cl●
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Ethane reacts with bromine in the presence of ultraviolet light to form tribromoethane and hydrogen bromide.
The reaction proceeds via free radical substitution involving initiation, propagation and termination steps.
Which equation represents a possible termination step in this reaction?
2C2H4● → C4H8
C2H4Br● + C2H5● → C4H9Br
C2H4● + C2H3Br● → C4H7Br
C2H3Br2● + C2H3Br● → C4H6Br3
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Heptane and octane can be separated in the school laboratory.
Which statement about the separation of a mixture of heptane and octane is correct?
Fractional distillation is used because the mixture is vapourised and the temperature gradient in the fractionation column allows the mixture to separate by boiling point
Octane will distil first as the strength of the van der Waals forces is weaker resulting in a lower boiling point
Heptane will distil first as the strength of the van der Waals forces is weaker resulting in a lower boiling point
Simple distillation is used because the mixture is vapourised and the temperature gradient in the fractionation column allows the mixture to separate by boiling point
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The cracking of hexadecane, C16H34, can produce heptane, cyclohexane and propene.
Which of the following is the correct information for the cracking described?
| Type of cracking | Temperature / K | Pressure / kPa | Catalyst |
A | Catalytic | 1000 | 100 | Zeolite |
B | Catalytic | 700 | 250 | Aluminosilicate |
C | Thermal | 1500 | 7000 | Aluminium oxide |
D | Thermal | 700 | 250 | Silicon dioxide |
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