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MCAT Chemistry Question — Standard Cell Potential

What is the standard cell potential for the spontaneous reaction below?

2 Ag(s) + Cl2(g) → 2 AgCl(s)


Eo (V)

Ag+ + e → Ag


Cl2 + 2 e → 2 Cl



A. –0.24 V
B. -0.56 V
C. +0.56 V
D. +2.16 V

Click for Explanation

This question asks the examinee to determine the standard cell potential for the spontaneous reaction between silver and chlorine gas. Choices A and B can be eliminated because the reaction is spontaneous and should thus have a positive cell potential. The standard cell potential is given by the equation Eocell = Eooxidation + Eoreduction. In the reaction above, silver metal is oxidized and chlorine gas is reduced. According to the table, the standard oxidation potential of Ag is -0.8 V and the standard reduction potential of Cl2 is equal to 1.36 V. Thus, Eocell = -0.8 V+ 1.36 V = 0.56 V, making choice C the correct answer.

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