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A solid appears when the concentration of a substance in solution rises past a certain point. What point is that?
AIts melting point in pure form
BIts boiling point in pure form
CIts molar mass in grams per mole
DIts solubility under those conditions
Answer & Solution
Correct answer: D. Its solubility under those conditions
1. Solubility fixes the largest concentration a solution can hold.
2. Once the concentration in solution exceeds that value, the excess can no longer stay dissolved.
3. The excess separates out as solid, which is precipitation.
4. Substances of low solubility reach that limit quickly, so they precipitate readily.
5. Melting and boiling points describe phase changes of the pure substance, not behaviour in solution.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.2 Classifying Chemical Reactions_
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