Calculate the free-energy change for the dissolution in...

Calculate the free-energy change for the dissolution in water of one mole of $\mathrm{NaBr}$ and one mole of $\mathrm{NaI}$ at $298 \mathrm{K}$ from the values in the following table. $$\begin{array}{lcc}\hline & \Delta H_{\text {solution }}^{\circ}(\mathrm{k} J / \mathrm{mol}) & \Delta S_{\text {solution }}^{\circ}[J /(\mathrm{mol} \cdot \mathrm{K})] \\\text { NaBr } & -0.60 & 57 \\\hline \text { Nal } & -7.5 & 74 \\\hline\end{array}$$

Calculate the free-energy change for the dissolution in water of one mole of $\mathrm{NaBr}$ and one mole of $\mathrm{NaI}$ at $298 \mathrm{K}$ from the values in the following table.
$$\begin{array}{lcc}\hline & \Delta H_{\text {solution }}^{\circ}(\mathrm{k} J / \mathrm{mol}) & \Delta S_{\text {solution }}^{\circ}[J /(\mathrm{mol} \cdot \mathrm{K})] \\\text { NaBr } & -0.60 & 57 \\\hline \text { Nal } & -7.5 & 74 \\\hline\end{array}$$

Key Concepts

Gibbs Free Energy

Gibbs free energy (?G) is the thermodynamic potential that indicates the maximum reversible work that may be performed by a thermodynamic system at constant temperature and pressure. It helps determine whether a process, such as dissolution, is spontaneous; if ?G is negative, the process is thermodynamically favorable.

Enthalpy Change

Enthalpy change (?H) represents the heat absorbed or released during a process at constant pressure. In the context of dissolution, it indicates whether the process is exothermic (releasing heat) or endothermic (absorbing heat), which can influence the behavior and solubility of the solute in the solvent.

Entropy Change

Entropy change (?S) measures the change in disorder or randomness in a system during a process. When a solute dissolves, the distribution of particles often becomes more random, which can contribute positively to the spontaneity of the dissolution process, particularly when temperature effects are taken into account.

Temperature's Role in Thermodynamics

Temperature plays a crucial role in thermodynamic calculations by modulating the impact of entropy on the free energy change. In the Gibbs free energy equation (?G = ?H - T?S), the temperature determines the magnitude of the T?S term, balancing against the enthalpy change to dictate whether a process, like dissolution, will occur spontaneously.

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