All Flashcards
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.
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 is the effect of a positive ΔG° on a reaction's spontaneity?
The reaction is nonspontaneous and requires an external energy source to proceed.
What is the effect of coupling a nonspontaneous reaction with a highly spontaneous reaction?
If the spontaneous reaction's negative ΔG° is large enough, the overall coupled reaction becomes spontaneous.
What is the effect of multiplying a reaction by a coefficient on its ΔG° value?
The ΔG° value is multiplied by the same coefficient.
What is the effect of adding two reactions together?
The ΔG° values of the two reactions are also added together to find the ΔG° of the overall reaction.
What is the effect of using an external power source on a nonspontaneous reaction in an electrolytic cell?
The external power source provides the necessary energy to drive the nonspontaneous reaction forward.