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Chapter 10: Problem 40

a. Use the following data to calculate the enthalpy of hydration for calcium chloride and calcium iodide. $$\begin{array}{|llc|} \hline & \text { Lattice Energy } & \Delta H_{\text {soln }} \\ \hline \mathrm{CaCl}_{2}(s) & -2247 \mathrm{kJ} / \mathrm{mol} & -46 \mathrm{kJ} / \mathrm{mol} \\ \mathrm{Cal}_{2}(s) & -2059 \mathrm{kJ} / \mathrm{mol} & -104 \mathrm{kJ} / \mathrm{mol} \\ \hline \end{array}$$ b. Based on your answers to part a, which ion, \(\mathrm{Cl}^{-}\) or \(\mathrm{I}^{-}\), is more strongly attracted to water?

Short Answer

Expert verified
The enthalpy of hydration for calcium chloride is \(2201 \ \text{kJ/mol}\) and for calcium iodide is \(1955 \ \text{kJ/mol}\). Since the enthalpy of hydration of calcium chloride is higher, the Cl- ion is more strongly attracted to water than the I- ion.

Step by step solution

01

Understand the enthalpy of hydration formula

The enthalpy of hydration is the change in enthalpy when one mole of a substance is dissolved in water to form an infinitely dilute solution. The enthalpy of hydration can be calculated as follows: \[ \Delta H_{\text{hyd}} = \Delta H_{\text{soln}} - \Delta H_{\text{lattice}} \]
02

Calculate the enthalpy of hydration for calcium chloride

Now let's calculate the enthalpy of hydration for calcium chloride using the given values: \[ \begin{aligned} \Delta H_{\text{hyd CaCl}_2} &= \Delta H_{\text{soln CaCl}_2} - \Delta H_{\text{lattice CaCl}_2} \\ &= (-46 \ \text{kJ/mol}) - (-2247 \ \text{kJ/mol}) \\ &= 2201 \ \text{kJ/mol} \end{aligned} \]
03

Calculate the enthalpy of hydration for calcium iodide

Now let's calculate the enthalpy of hydration for calcium iodide using the given values: \[ \begin{aligned} \Delta H_{\text{hyd CaI}_2} &= \Delta H_{\text{soln CaI}_2} - \Delta H_{\text{lattice CaI}_2} \\ &= (-104 \ \text{kJ/mol}) - (-2059 \ \text{kJ/mol}) \\ &= 1955 \ \text{kJ/mol} \end{aligned} \]
04

Determine which ion, Cl- or I-, is more strongly attracted to water

Based on the enthalpy of hydration values calculated in steps 2 and 3, we can now compare the ions. The enthalpy of hydration of calcium chloride is higher than that of calcium iodide: \(2201 \ \text{kJ/mol} > 1955 \ \text{kJ/mol}\). This means that the Cl- ion is more strongly attracted to water molecules than the I- ion due to the higher negative enthalpy associated with the process.

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Most popular questions from this chapter

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