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Ch.13 - Solutions & Their Properties
All textbooksMcMurry 8th EditionCh.13 - Solutions & Their PropertiesProblem 89
Chapter 13, Problem 89

When solid CaCl2 is added to liquid water, the temperature rises. When solid CaCl2 is added to ice at 0 °C, the temperature falls. Explain.

Verified step by step guidance
1
Step 1: Understand the process of dissolving CaCl2 in water. When solid calcium chloride (CaCl2) is added to water, it dissolves and dissociates into its ions, Ca²⁺ and Cl⁻. This process is exothermic, meaning it releases heat, which causes the temperature of the water to rise.
Step 2: Consider the dissolution of CaCl2 in ice. When CaCl2 is added to ice at 0 °C, it also dissolves, but the situation is different because the ice must first melt to allow the dissolution process to occur.
Step 3: Recognize the energy requirement for melting ice. The melting of ice requires energy (endothermic process), which is absorbed from the surroundings, including the CaCl2 and the ice itself, causing the temperature to fall.
Step 4: Analyze the net effect. In the case of ice, the energy absorbed to melt the ice can be greater than the energy released by the dissolution of CaCl2, resulting in an overall temperature decrease.
Step 5: Summarize the contrasting effects. In liquid water, the exothermic dissolution of CaCl2 increases the temperature, while in ice, the endothermic melting process dominates, leading to a temperature decrease.
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