Crude oil is a mixture mainly made up of which type of compound?
Hydrocarbons
Carbohydrates
Metal oxides
Alcohols
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WhyCrude oil is a complex mixture of hydrocarbons, which are compounds made of hydrogen and carbon atoms only.
2Multiple choice · Easy
What is the general formula for the alkanes?
CnH2n+2
CnH2n
CnHn
CnH2n-2
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WhyAlkanes are saturated hydrocarbons that follow the general formula CnH2n+2, so for example methane is CH4 and ethane is C2H6.
3Multiple choice · Easy
Which of these is the molecular formula of methane, the first member of the alkanes?
CH4
C2H6
C2H4
CH3
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WhyMethane has one carbon atom bonded to four hydrogen atoms, giving the formula CH4.
4Multiple choice · Easy
Crude oil is separated into useful fractions using which process?
Fractional distillation
Filtration
Crystallisation
Electrolysis
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WhyFractional distillation separates crude oil into fractions because the different hydrocarbons have different boiling points.
5Multiple choice · Easy
Which two products are formed when a hydrocarbon undergoes complete combustion?
Carbon dioxide and water
Carbon monoxide and hydrogen
Carbon and water
Carbon dioxide and hydrogen
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WhyComplete combustion of a hydrocarbon produces carbon dioxide and water, releasing energy.
6Fill in the blank · Easy
Crude oil is described as a resource because it is being used up much faster than it is formed.
Answer:
finite / non-renewable
WhyCrude oil takes millions of years to form, so on a human timescale it is non-renewable (finite).
7Multiple choice · Medium
In fractional distillation of crude oil, where are the fractions with the lowest boiling points collected?
Near the top of the column where it is coolest
Near the bottom of the column where it is hottest
In the middle of the column
They are removed as a liquid before heating
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WhySmaller molecules have lower boiling points; they rise to the cooler top of the fractionating column before condensing.
8Multiple choice · Medium
As the size of a hydrocarbon molecule increases, how do its properties change?
Boiling point increases and viscosity increases
Boiling point decreases and viscosity increases
Boiling point increases and flammability increases
Boiling point decreases and viscosity decreases
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WhyLarger hydrocarbons have higher boiling points, are more viscous, are less flammable and are less easily ignited.
9Multiple choice · Medium
Cracking is used to convert larger hydrocarbon molecules into smaller ones mainly because:
There is greater demand for shorter-chain hydrocarbons than supply
Longer hydrocarbons burn more cleanly
Shorter hydrocarbons have higher boiling points
Longer hydrocarbons are gases at room temperature
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WhyCracking breaks long-chain hydrocarbons into shorter, more useful molecules such as petrol and into alkenes for making polymers; demand for short chains is higher than supply.
10Multiple choice · Medium
Which test can be used to distinguish an alkene from an alkane?
Bromine water, which is decolourised by alkenes
Limewater, which turns milky with alkenes
Universal indicator, which turns red with alkenes
A glowing splint, which relights with alkenes
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WhyAlkenes decolourise orange bromine water because the C=C double bond reacts with it in an addition reaction; alkanes do not.
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Organic compound: A compound built around carbon atoms, usually also containing hydrogen and sometimes other elements such as oxygen.
Crude oil: A thick, dark mixture of many different hydrocarbons formed over millions of years from the buried remains of ancient sea organisms.
Finite resource: A natural material such as crude oil that is being used up far faster than it forms and so will eventually run out.
Hydrocarbon: A compound made of hydrogen and carbon atoms only.
Homologous series: A family of compounds that share the same general formula and similar chemical properties, with each member differing from the next by CH2.
General formula: A formula that shows the ratio of atoms for any member of a homologous series, such as CnH2n+2 for alkanes.
Alkane: A saturated hydrocarbon with the general formula CnH2n+2 containing only single carbon-carbon bonds.
Saturated compound: A compound whose carbon atoms are joined only by single bonds, so it contains the maximum number of hydrogen atoms.