A mixture contains solid iodine and solid potassium iodide. Iodine is slightly soluble in water, while potassium iodide is very soluble. Which method is most appropriate to separate and purify the iodine?
Show the answer and explanation
Correct answer
C. Heat the mixture to sublime the iodine and collect it on a cold surface
Principle or equation
Iodine sublimes when heated, changing directly from solid to gas, while potassium iodide does not sublime. Sublimation can separate a sublimable solid from a non-sublimable one.
Why this answer is correct
Heating the mixture causes iodine to sublime; the purple vapor can be condensed on a cold surface, leaving potassium iodide behind. This is a direct and efficient method. Adding water would dissolve potassium iodide and also some iodine, making separation less effective. Ethanol would dissolve both, not separating them.
Example
I2(s) → I2(g) → I2(s) (on cold surface)
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