Question

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Which two values for ∆G and E0cell correctly indicate a spontaneous reaction? A) ∆G = -89 kJ, E0cell = -0.46 v B) ∆G = -89 kJ, E0cell = +0.46 v C) ∆G = +89 kJ, E0cell = -0.46 v D) ∆G = +89 kJ, E0cell = +0.46 v

Answer 1

for a reaction to be spontaneous, ΔG has to be negative and E° cell is positive. 

the answer is B

Answer 2

Answer: Choice B is correct. $\Delta G=-89kJ$ and $E^0_c_e_l_l=+0.46V$

Explanation: $\Delta G$ stands for Gibbs free energy equation. A reaction is spontaneous if $\Delta G$ is negative and the reaction non spontaneous if $\Delta G$ is positive.

For a cell, $\Delta G$ is calculated from the cell potential using the equation:

$\Delta G=-nFE^0_c_e_l_l$

where, n is the moles of electrons transferred in a balanced equation, F is the faraday constant and $E^0_c_e_l_l$ is standard cell potential.

From the above equation, $\Delta G$ could only be negative if $E^0_c_e_l_l$ is positive as the equation has negative sign.

So, the only correct choice is the one for which $E^0_c_e_l_l$ is positive and $\Delta G$ is negative.

Hence. choice B is correct.