Which fo the following expression defines the physical siginificance of Gibbos energy change

Options

A. `Delta G = W ("exp")`
B. `Delta (G) = W ("nonexp")`
C. `Delta G = - W ("exp")`
D. `- Delta G = W ("nonexp")`

Answer

D

Explanation

A knowledge of the magnitude of the free enegy change of a chemical reaction allows the predicition of the useful work (other than pressure -voume work or expanision work) that can be extracted from it. It can be shown that a decrease in Gibbs energy for a process is equal to the maximum possible useful work that can be derived fromk the process, i.e.,
`- Delta G = W_(max)`
for a reversible change at constant `T` and `P`. In case of galvanic cells (chapter 8), Gibbs energy change, `Delta G`, is related to the electrical worik done by the cell. If `E` is the emf of the cell and `n` moles of electrons are involved, the electrical work will be equal to `nFE` (where `F` is the Faraday constant). Thus.
`Delta_(r) G = - nFE_(cell)`
If the reactants and products are in their standard states, then
`Delta_(r) G^(@) = - nFE_(cell)^(@)`
Here, `E_(cell)^(@)` is the standard cell potential.