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. If it melts at a single temperature.
- B. If it melts at multiple temperatures.
- C. If it has a boiling point.
- D. If it is a solid at room temperature.
Answer
The correct answer is If it melts at a single temperature.. 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 If it melts at a single temperature.. 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
Identifying Purity from Melting Points
Students often think that a substance is pure if it has a melting point that matches the literature value, without considering the possibility of impurities affecting the melting point.
Students should remember that impurities can lower or raise the melting point, and they should analyze the melting point range to determine purity.
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