Types of formula for organic molecules

3 marks · Normal

Explain how the displayed and molecular formulae of an organic molecule are different. Use an example in your answer.

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

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Also accept: Any correct comparison using a valid hydrocarbon example

Common mistakes: Confusing displayed with structural formula; Not using an example

Show mark scheme and worked solution

Marking points

M1 · 1 mark · States that molecular formula shows numbers of atoms only.

M2 · 1 mark · States that displayed formula shows all atoms and all bonds.

B1 · 1 mark · Provides a correct example to illustrate.

Worked solution

The molecular formula of a molecule tells you the number of each type of atom present, for example, ethene is C2H4.

The displayed formula shows every atom and bond in the structure. For ethene, the displayed formula is:

So the displayed formula gives you more structural detail, showing how atoms are connected, while the molecular formula just gives the count.