Alkanes and structural isomerismEdexcel International A Level Chemistry: Flashcards

What these 13 flashcards ask

What is a hydrocarbon?
What does saturated mean?
State the general formula of the alkanes.
State the general formula of the cycloalkanes.
Why does a cycloalkane have two fewer hydrogen atoms than the alkane with the same number of carbon atoms?
What are structural isomers?
How many structural isomers does C₄H₁₀ have, and what are they?
Name the three isomers of C₅H₁₂.
Name the five isomers of C₆H₁₄.
Name two structural isomers of C₄H₈ that are cycloalkanes.
What is the molecular formula of octane?
How do you start finding all isomers of an alkane?
Why is a methyl branch on carbon 1 not a new isomer?

Exam questions on Alkanes and structural isomerism

Petrol is a mixture of hydrocarbons including pentane, octane and cyclohexane. A refinery chemist classifies each of these compounds as an alkane or a cycloalkane.
Explain what is meant by the terms 'hydrocarbon' and 'saturated' when they are applied to octane.2 marks
Pentane, C₅H₁₂, is a liquid in petrol that boils at 36 °C. A refinery sample of C₅H₁₂ is found to contain two other compounds with the same molecular formula, which boil at 28 °C and 10 °C.
Explain why the compound that boils at 28 °C, 2-methylbutane, is a structural isomer of pentane.2 marks
A hydrocarbon X is found in petrol. Analysis shows that it contains 83.3% carbon and 16.7% hydrogen by mass, and its relative molecular mass is 72.0. X does not decolourise bromine water and contains no carbon–carbon double bonds.
Use the data to deduce the empirical formula and the molecular formula of X, showing your working.3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).