DSE Chemistry

DSE Chemistry: Fossil Fuels and Carbon Compounds — Practice Questions & Answers

Fossil fuels and their combustion, the homologous series concept, the chemistry of alkanes and alkenes, addition reactions, and structural isomerism.

258 practice questions available for this topic — here are 10 with full answers and explanations.

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Practice questions with answers

1 Multiple choice · Medium

One mole of methane is allowed to react with two moles of chlorine in the presence of light. Which best describes the organic product(s)?

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WhyChlorination of methane occurs stepwise, giving a mixture of all four chloromethanes.
2 Multiple choice · Medium

The reaction of methane with chlorine under ultraviolet light is classified as a

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WhyHydrogen atoms are substituted by chlorine atoms.
3 Multiple choice · Hard

Why does ethene, unlike methane, react with chlorine without UV light?

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WhyEthene undergoes rapid addition across its C=C bond, whereas methane needs UV for substitution.
4 Fill in the blank · Easy

Replacing hydrogen atoms of an alkane with chlorine atoms under light is a reaction.

Answer: substitution

WhyIt is a photochemical substitution.
5 Fill in the blank · Medium

Alkanes contain only single bonds, so they are hydrocarbons.

Answer: saturated

WhySaturated hydrocarbons have no C=C bonds.
6 Fill in the blank · Hard

The condition required for the reaction between methane and chlorine is light.

Answer: ultraviolet / UV

WhyUV light initiates the substitution.
7 Multiple choice · Medium

Petrol can be obtained from petroleum by fractional distillation. At the molecular level this works because the hydrocarbon molecules in petroleum have

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Whydifferent chain lengths and therefore different boiling points.
8 Multiple choice · Easy

Besides fractional distillation, extra petrol can be produced from heavier fractions by

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Whycracking.
9 Multiple choice · Hard

Larger hydrocarbon molecules have higher boiling points because

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Whythey have more electrons, giving stronger van der Waals forces between molecules.
10 Fill in the blank · Medium

Fractional distillation separates petroleum into fractions according to differences in point.

Answer: boiling

WhyBoiling point.

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Key terms in Fossil Fuels and Carbon Compounds

Fossil fuel: A fuel such as coal, petroleum or natural gas formed from the remains of ancient organisms.
Petroleum: A naturally occurring mixture of hydrocarbons, also called crude oil.
Hydrocarbon: A compound that contains only carbon and hydrogen atoms.
Fractional distillation: A process that separates crude oil into fractions according to their boiling point ranges.
Fraction: A group of hydrocarbons with similar boiling points collected during distillation of crude oil.
Alkane: A saturated hydrocarbon with only single carbon-carbon bonds and general formula CnH2n+2.
Alkene: An unsaturated hydrocarbon containing a carbon-carbon double bond and general formula CnH2n.
Saturated compound: An organic compound containing only single bonds between carbon atoms.

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Practise other DSE Chemistry topics

Topic A: Planet Earth Topic B: Microscopic World I Topic C: Metals Topic D: Acids and Bases Topic F: Microscopic World II Topic G: Redox Reactions, Chemical Cells and Electrolysis Topic H: Chemical Reactions and Energy Topic I: Rate of Reaction Topic J: Chemical Equilibrium Topic K: Chemistry of Carbon Compounds Topic L: Patterns in the Chemical World Topic M: Industrial Chemistry (Elective) Topic N: Materials Chemistry (Elective) Topic O: Analytical Chemistry (Elective)