Which of the following criteria indicate that a reaction is SPONTANEOUS? Check all that apply.
a) The change in free energy is positive.
b) The entropy of the universe decreases.
c) The change in free energy is negative.
d) The entropy of the system increases.
e) The entropy of the system decreases.
f) The entropy of the universe increases.
I know C and F are correct but I don't know about the rest. I am confuse with D and E.
C is correct. I don't understand why F is also true; in fact, isn't F true regardless of the reaction. I understand that the entropy of the universe is increasing and there is no mention of a reaction.
But do you think that D and E make any reaction spontaneous?
To determine which criteria indicate that a reaction is spontaneous, let's analyze each option:
a) The change in free energy is positive.
In a spontaneous reaction, the change in free energy (ΔG) is negative, not positive. When ΔG is negative, the reaction releases energy and is considered thermodynamically favorable.
b) The entropy of the universe decreases.
In a spontaneous reaction, the second law of thermodynamics states that the entropy of the universe (ΔS_universe) must increase. If the entropy of the universe decreases, it indicates a non-spontaneous process.
c) The change in free energy is negative.
Correct. As mentioned earlier, a negative ΔG indicates that the reaction is spontaneous.
d) The entropy of the system increases.
In a spontaneous reaction, the entropy of the system (ΔS_system) can either increase or decrease. There is no specific requirement for the entropy of the system to increase for a reaction to be spontaneous.
e) The entropy of the system decreases.
Generally, an increase in entropy contributes to a spontaneous reaction. However, it is not an absolute requirement. A reaction can be spontaneous even if the entropy of the system decreases, as long as the overall entropy of the universe increases.
f) The entropy of the universe increases.
Correct. In a spontaneous process, the entropy of the universe always increases. This implies that the overall tendency of the system and its surroundings is to become more disordered.
In conclusion, the correct criteria for indicating that a reaction is spontaneous are:
- The change in free energy is negative (c).
- The entropy of the universe increases (f).