Multiple Choice
Which of the following aqueous solutions has the lowest freezing point?
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14. Solutions
Freezing Point Depression
Multiple Choice
Which of the following will cause liquid water to freeze and become ice?
A
Lowering the temperature below 0 ^ext{o}C
B
Adding sodium chloride (NaCl) to water at 0 ^ext{o}C
C
Adding sugar to water at 0 ^ext{o}C
D
Increasing the pressure above atmospheric pressure at 0 ^ext{o}C
Verified step by step guidance1
Understand the phase change of water: water freezes and becomes ice when its temperature drops below its freezing point, which is 0 \^\{\text{o}\}C at standard atmospheric pressure.
Recognize that lowering the temperature below 0 \^\{\text{o}\}C removes thermal energy from the water, allowing the molecules to arrange into a solid crystalline structure (ice).
Consider the effect of adding sodium chloride (NaCl): salt lowers the freezing point of water (freezing point depression), so adding NaCl actually prevents freezing at 0 \^\{\text{o}\}C.
Consider the effect of adding sugar: like salt, sugar also lowers the freezing point of water, so it will not cause water to freeze at 0 \^\{\text{o}\}C.
Consider the effect of increasing pressure: for water, increasing pressure at 0 \^\{\text{o}\}C tends to favor the liquid phase rather than ice, so it does not cause freezing under these conditions.
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