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title: "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?"
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url: "https://nerd-notes.com/ubq/121476/"
date_modified: "2026-08-23T05:04:46+00:00"
---

# 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?

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?

- **A.** The calculated \(\Delta H_{\text{soln}}\) will be more negative than the true value because the heat lost to the surroundings lowers the heat capacity of the solution, causing the calculated \(|q_{\text{rxn}}|\) to be too large.
- **B.** The calculated \(\Delta H_{\text{soln}}\) will be more negative than the true value because the lower final temperature recorded by the thermometer leads to an overestimated magnitude for \(q_{\text{rxn}}\).
- **C.** The calculated \(\Delta H_{\text{soln}}\) will be less negative than the true value because energy transferred to the surroundings results in a smaller measured \(\Delta T\), underestimating the magnitude of \(q_{\text{rxn}}\).
- **D.** The calculated \(\Delta H_{\text{soln}}\) will be less negative than the true value because the heat lost to the surroundings decreases the rate of dissolution, leaving a portion of \(\text{CaCl}_2(s)\) undissolved.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/121476/*