A pharmaceutical company produces a painkiller tablet. Each tablet contains exact quantities of an active ingredient, a binding agent and a coating substance. Explain why the painkiller tablet is described as a formulation rather than a pure substance, and explain how melting point data could be used to confirm that the active ingredient on its own is a pure substance.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A pharmaceutical company produces a painkiller tablet. Each tablet contains exact quantities of an active ingredient, a binding agent and a coating substance.
Model answer (5 marks)
A formulation is a mixture designed for a particular use; the tablet contains more than one substance.
The components are mixed in exact, carefully measured quantities.
The tablet is not a pure substance because it contains more than one compound – a mixture of substances not chemically bonded together.
A pure substance has a sharp, specific melting point – it melts at one exact temperature.
If the active ingredient is pure, its measured melting point will match the expected or known melting point exactly and will not melt over a range of temperatures.
The components are mixed in exact, carefully measured quantities.
The tablet is not a pure substance because it contains more than one compound – a mixture of substances not chemically bonded together.
A pure substance has a sharp, specific melting point – it melts at one exact temperature.
If the active ingredient is pure, its measured melting point will match the expected or known melting point exactly and will not melt over a range of temperatures.
Examiner tips
- Use the term ‘formulation’ and explain it’s a mixture. Mention exact quantities and lack of chemical bonding. State that a pure substance has a sharp melting point. Show that matching the known melting point confirms purity.
Common mistakes
- Calling the tablet a pure substance. Forgetting to mention the exact quantities of each component. Saying the melting point is ‘high’ or ‘low’ instead of ‘sharp’ and ‘matches known value’.
Mark scheme (5 marks)
- A formulation is a mixture designed for a particular use / the tablet contains more than one substance
- The components are mixed in exact / carefully measured quantities
- The tablet is not a pure substance because it contains more than one compound / it contains a mixture of substances not chemically bonded together
- A pure substance has a sharp / specific melting point (melts at one exact temperature)
- If the active ingredient is pure, its measured melting point will match the expected / known melting point exactly / will not melt over a range of temperatures
Key terms in this question
formulation · pure substance · melting point data
Related
- All Eduqas A-Level Chemistry revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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