Which of the following statements about standard reduction potential and spontaneity are true?
choose one or more:
a. a reaction with a negative gibbs standard free energy is thermodynamically spontaneous under standard conditions.
b. a coupled redox reaction with a negative standard reduction potential is thermodynamically spontaneous.
c. a coupled redox reaction with a positive standard reduction potential îeââ² is thermodynamically spontaneous.
d. a reaction with a positive gibbs standard free energy is thermodynamically spontaneous under standard conditions.

Statements A and C are true.      

Explanation:

Let's evaluate the given statements:

A) A reaction with negative Gibbs standard free energy (ΔG) will result in a reaction thermodynamically spontaneous, under standard conditions, by the Nernst equation:  

       (1)

where n: is the number of electrons transferred in the cell reaction, F: is the Faraday constant and E: is the cell potential

For an electrochemical reaction to be spontaneous, that is to say, in a galvanic cell, the change in Gibbs free energy must be negative. From equation (1), we have that a negative ΔG will result in a spontaneous electrochemical reaction.  

Hence, statement A is correct, and D is incorrect.

C) A coupled redox reaction with a positive standard reduction potential is thermodynamically spontaneous:  

On equation (1), for the Gibbs free energy to be negative and, therefore, the reaction to be thermodynamically spontaneous, the standard reduction potential must be positive.    

Hence, statement C is correct, and B is incorrect.    

I hope it helps you!  

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