electromotive force

[RySerr21]

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Given that the standard reduction potentials for Sm^3+ and [RhCl6]^3- are -2.41 V and 0.44 V, calculate the EMF of the following reaction:

[Sm^3+] + Rh + [RhCl6]^3- + Sm


Looking at the equation, Sm^3+ is reduced and Rh is oxidized. So we use the Sm^3+ reduction potential as is and we flip the reduction potential for Rh

EMF: -2.41 + (-0.44) = -2.85

Therefore, the cell is electrolytic. From this result, it is evident that the reaction would proceed spontaneously to the left, in which case the Sm would be oxidized while [RhCl6]^3- would be reduced.

Can someone explain the bolded part? I understand the rest. I dont understand why they concluded that because it is electrolytic, it must proceed to the left. Is it because, as written (to the right), it is electrolytic, which is non-spontaneous reaction. So, to make it a spontaneous reaction, you have make it go to the left?

 

[BerkReviewTeach]

Therefore, the cell is electrolytic. From this result, it is evident that the reaction would proceed spontaneously to the left, in which case the Sm would be oxidized while [RhCl6]^3- would be reduced.

Can someone explain the bolded part? I dont understand why they concluded that because it is electrolytic, it must proceed to the left. Is it because, as written (to the right), it is electrolytic, which is non-spontaneous reaction. So, to make it a spontaneous reaction, you have make it go to the left?

You answered your own question. Electrolytic reactions are unfavorable in the forward direction (-emf correlates to a +?G). A reaction that is unfavorable in the forward direction is one that is favorable in the reverse direction. They have chosen to use the word spontaneous instead of "favorable" and to the left instead of "the reverse direction."

 

[RySerr21]

You answered your own question. Electrolytic reactions are unfavorable in the forward direction (-emf correlates to a +?G). A reaction that is unfavorable in the forward direction is one that is favorable in the reverse direction. They have chosen to use the word spontaneous instead of "favorable" and to the left instead of "the reverse direction."

haha okay. for some reason while typing the question it sort of came to me, but i figured i'd finish posting it anyway just in case i was wrong. thanks!! 👍