The formula for standard Gibbs free energy change is ; ΔG° = ΔH° - TΔS°
ΔG must be negative in order for a response to be possible.
ΔH could be either positive or negative (an exothermic reaction) (an endothermic reaction). ΔS could also be good or negative in a similar way.
The signs of "H" and "S" can be put together in one of four ways.
ΔH is adverse and ΔS is favorable.
No matter the temperature, both terms are (-)ve, thus G must likewise be (-)ve. All temperatures will allow for the reaction.
<h3>What is Standard Potential ?</h3>
A measurement of the potential for equilibrium is the standard electrode potential. The potential of the electrode is the difference in potential between the electrode and the electrolyte.
<h3>1. When the ΔH is negative and ΔS is positive ; </h3>
ΔG = ΔH - TΔS
ΔH is negative.
TΔS is (+)ve, and -TΔS is (-)ve.
Both terms are (-)ve irrespective of the temperature, and ΔG is also bound to be (-)ve.
<h3>2. When the ΔH is positive and ΔS is negative ;</h3>
ΔG = ΔH - TΔS
ΔH is (+)ve. TΔS is negative, and so -TΔS is (-)ve.
Both terms are positive irrespective of the temperature, and ΔG is also bound to be positive. This reaction will not be feasible at any temperature.
<h3>3 . When the ΔH is positive and ΔS is positive ; </h3>
ΔG = ΔH - TΔS
ΔH is (+)ve. TΔS is positive, and so -TΔS is (-)ve.
The increasing temp will change the equation.
At the high temp, -TΔS will become more and more (-)ve, and will eventually outweigh the effect of ΔH.
The reaction won't be feasible at low temp, but if you heat it, there will be a temp at which it becomes feasible, because ΔG becomes (-)ve.
The decomposition of CaC03 is an example of this.
<h3>4. When the ΔH is negative and ΔS is negative ; </h3>
ΔG = ΔH - TΔS
ΔH is (-)ve. TΔS is negative, and so -TΔS is (+)ve.
There will be a effect on temperature. As temperature increases, -TΔS will become more (+)ve.
At the low temperatures, ΔG will be (-)ve because of the effect of (-)ve ΔH.
As we increase the temp, the effect of the positive -TΔS will eventually outweigh that.
The value of the ΔG will become (-)ve.
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