AP Chemistry
6.6 Introduction to Enthalpy of Reaction
6.4 Heat Capacity and Calorimetry
A student investigates the thermodynamics of dissolution by dissolving a sample of \(\text{CaCl}_2(s)\) in water using a coffee-cup calorimeter. The dissolution process is exothermic, as represented by the equation below:
\[ \text{CaCl}_2(s) \rightarrow \text{Ca}^{2+}(aq) + 2\,\text{Cl}^-(aq) \quad \Delta H_{\text{soln}} < 0 \]
The student measures the initial temperature of \(100.0 \text{ g}\) of distilled water, adds \(5.55 \text{ g}\) of \(\text{CaCl}_2(s)\), stirs until the solid completely dissolves, and records the maximum temperature reached. The student computes \(\Delta H_{\text{soln}}\) assuming the calorimeter is an isolated system. If a significant quantity of thermal energy was lost to the surrounding air during the trial, which of the following correctly predicts the effect on the calculated value of \(\Delta H_{\text{soln}}\) and provides the correct justification?
\[ \text{CaCl}_2(s) \rightarrow \text{Ca}^{2+}(aq) + 2\,\text{Cl}^-(aq) \quad \Delta H_{\text{soln}} < 0 \]
The student measures the initial temperature of \(100.0 \text{ g}\) of distilled water, adds \(5.55 \text{ g}\) of \(\text{CaCl}_2(s)\), stirs until the solid completely dissolves, and records the maximum temperature reached. The student computes \(\Delta H_{\text{soln}}\) assuming the calorimeter is an isolated system. If a significant quantity of thermal energy was lost to the surrounding air during the trial, which of the following correctly predicts the effect on the calculated value of \(\Delta H_{\text{soln}}\) and provides the correct justification?
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