Which of the following statements is true?
All spontaneous processes are exothermic
All non-spontaneous processes are exothermic
All spontaneous processes release free energy***
Entropy always increases in a spontaneous process
All spontaneous processes are exothermic
The statement that is true is: All spontaneous processes release free energy.
The true statement is: All spontaneous processes release free energy.
To understand why this statement is true, let's explain the concept of spontaneity and free energy.
Spontaneous processes are those that occur naturally without requiring any external intervention. In other words, they happen on their own. On the other hand, non-spontaneous processes require an input of energy to occur.
Free energy is a measure of the energy available to do useful work in a system. It takes into account both the energy of the system and the entropy, which is a measure of disorder or randomness. The equation for free energy, known as Gibbs free energy, is given by:
ΔG = ΔH - TΔS
Here, ΔG represents the change in free energy, ΔH is the change in enthalpy (heat transfer), T is the temperature in Kelvin, and ΔS is the change in entropy.
Now, let's analyze the statements:
1. All spontaneous processes are exothermic: This statement is not true. Spontaneous processes can be either exothermic (release heat) or endothermic (absorb heat).
2. All non-spontaneous processes are exothermic: This statement is also not true. Non-spontaneous processes can be either exothermic or endothermic, depending on the specific conditions.
3. All spontaneous processes release free energy: This statement is true. For a process to be spontaneous, the change in free energy (ΔG) must be negative. This means that the system releases free energy and can do useful work.
4. Entropy always increases in a spontaneous process: This statement is generally true. In many spontaneous processes, the entropy of the system increases, leading to a positive change in entropy (ΔS). However, there are some exceptions where the entropy remains constant or decreases, but these cases are relatively rare.
Therefore, the correct statement is that all spontaneous processes release free energy.