Question detail
Which answer avoids confusing pure substance with another qualitative analysis result?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Purity, formulations and chromatography
Question
- A. A mixture of two or more elements.
- B. A single element or compound not mixed with any other substance.
- C. A substance that can vary in composition.
- D. A solution that contains dissolved impurities.
Answer
The correct answer is A single element or compound not mixed with any other substance.. It matches pure substance because the evidence is single element or compound / fixed melting point and the expected result is purity evidence.
Explanation
The correct option is A single element or compound not mixed with any other substance.. Use this as an exam check: if the observation is not purity evidence, the conclusion about pure substance is not properly supported. Other options are weaker when they confuse gas tests, flame colours, ion-test precipitates, chromatography evidence, or pure-substance/formulation wording.
Common mistake
Impurities and Melting/Boiling Points
Students often think that impurities only affect the boiling point of a substance, ignoring their impact on the melting point.
Remember that impurities can change both the melting point and boiling point of a substance, causing them to be lower than those of the pure substance.
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