Question detail
For Purity, formulations and chromatography, which option uses the correct Chemical analysis evidence for pure substance?
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. They can have varying melting points.
- B. They melt and boil at specific temperatures.
- C. They are always solid at room temperature.
- D. They are mixtures of different compounds.
Answer
The correct answer is They melt and boil at specific temperatures.. 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 They melt and boil at specific temperatures.. This response is stronger than the distractors because it keeps the test, observation, and interpretation in the correct order for pure substance. Other options are weaker when they confuse gas tests, flame colours, ion-test precipitates, chromatography evidence, or pure-substance/formulation wording.
Common mistake
Misunderstanding Pure Substances
Students often think that a pure substance can contain small amounts of impurities and still be considered pure.
A pure substance must be a single element or compound with no other substances mixed in.
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