Which of the following favor the spontaneous formation of a solution?
Select all that apply:
An increase in the disorder of a system
An increase in the internal energy of a system
A decrease in the internal energy of a system
A decrease in the disorder of a system
The correct answer and explanation is:
The correct answers are:
- An increase in the disorder of a system
- A decrease in the internal energy of a system
Explanation:
The spontaneity of a process, such as the formation of a solution, is determined by the change in Gibbs free energy (ΔG). The equation for Gibbs free energy is: ΔG=ΔH−TΔS\Delta G = \Delta H – T\Delta S
where:
- ΔH\Delta H is the change in enthalpy (heat energy).
- TT is the absolute temperature.
- ΔS\Delta S is the change in entropy (disorder).
For a solution to form spontaneously, the overall change in Gibbs free energy must be negative (ΔG<0\Delta G < 0).
- An increase in the disorder of a system: This favors spontaneity. When a solution forms, the mixing of solute and solvent typically increases the disorder (or entropy, ΔS\Delta S). A positive ΔS\Delta S contributes to making ΔG\Delta G negative, favoring spontaneity.
- A decrease in the internal energy of a system: This also favors spontaneity. A decrease in internal energy (ΔH\Delta H) generally makes ΔG\Delta G more negative, especially if the temperature is high. For example, the process of dissolving a substance might release energy (exothermic process), which decreases the system’s internal energy and supports the spontaneous formation of a solution.
- An increase in the internal energy of a system: This does not favor spontaneity. When the internal energy increases, the system tends to become less stable. If ΔH\Delta H is positive (endothermic process), it makes ΔG\Delta G less negative, reducing the likelihood of spontaneous solution formation.
- A decrease in the disorder of a system: This also does not favor spontaneity. A decrease in disorder (negative ΔS\Delta S) would make ΔG\Delta G more positive, thus hindering the spontaneous formation of a solution.
In summary, the formation of a solution is spontaneous if the system’s entropy increases and its internal energy decreases, leading to a negative change in Gibbs free energy.