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.