A mixture contains solid iodine and solid sodium chloride. Iodine sublimes readily when heated gently, while sodium chloride does not. Which method is most appropriate to separate and obtain pure iodine from the mixture?
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Correct answer
B. Heat the mixture gently and collect the sublimed iodine on a cold surface
Principle or equation
Sublimation is a separation technique for substances that can change directly from solid to gas upon heating, leaving non-sublimable impurities behind.
Why this answer is correct
Iodine sublimes when heated, forming purple vapor that can be collected and cooled back to solid on a cold surface. Sodium chloride does not sublime, so it remains in the container. This directly separates and purifies iodine.
Example
A mixture of iodine and sand can be separated by heating; iodine vapor condenses on a cold watch glass, leaving sand behind.
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