All Flashcards
Define 'thermodynamically favorable reaction'.
A reaction that occurs spontaneously, with ΔG° < 0 and K > 1.
Define 'thermodynamically unfavorable reaction'.
A reaction that does not occur spontaneously, with ΔG° > 0 and K < 1.
Define 'electrolytic cell'.
A cell that uses electrical energy to drive a nonspontaneous redox reaction.
Define 'coupled reactions'.
Reactions that involve a nonspontaneous reaction and a spontaneous reaction that share a common intermediate, allowing the nonspontaneous reaction to proceed.
Define 'common intermediate'.
A substance produced in one step of a reaction mechanism and consumed in a later step.
What are the key differences between thermodynamically favorable and unfavorable reactions?
Favorable: ΔG° < 0, K > 1, spontaneous | Unfavorable: ΔG° > 0, K < 1, nonspontaneous.
What are the differences between voltaic and electrolytic cells?
Voltaic: Spontaneous redox reaction, produces electricity | Electrolytic: Nonspontaneous redox reaction, requires electricity.
Describe the process of using an electrolytic cell to drive a nonspontaneous reaction.
An external source of electricity provides energy to force a nonspontaneous redox reaction to occur.
Describe the process of extracting copper using coupled reactions.
Couple the nonspontaneous reaction Cu2S → 2Cu + S with the spontaneous reaction S + O2 → SO2. The overall reaction Cu2S + O2 → 2Cu + SO2 becomes spontaneous.
Describe the general process of coupled reactions.
A nonspontaneous reaction is paired with a spontaneous reaction that releases energy. These reactions share a common intermediate, and the overall ΔG° is negative, making the overall reaction spontaneous.
Outline the steps to calculate ΔG° for a coupled reaction.
- Identify the individual reactions and their ΔG° values. 2. If necessary, multiply reactions to cancel intermediates. Multiply the ΔG° value by the same factor. 3. Add the reactions and their corresponding ΔG° values to obtain the overall reaction and its ΔG°.
Describe the role of ATP in coupled reactions in biological systems.
The conversion of ATP to ADP releases energy, which is coupled with other reactions in biological systems to allow cells to perform work.