Page 1 of 1

Spontaneity

Posted: Fri Feb 28, 2020 4:17 pm
What determines whether a reaction is spontaneous or not? Is it based on whether the change in molar Gibbs free energy is positive or negative?

Re: Spontaneity

Posted: Fri Feb 28, 2020 4:23 pm
When delta G is negative, the reaction is spontaneous, and when delta G is positive, the reaction is nonspontaneous. However, in terms of potentials differences (E), when the value is postive, the cell reaction is spontaneous, and when the value is negatvie, the cell reaction is nonspontaneous. This is because of the equation deltaG= -nFEcell.

Re: Spontaneity

Posted: Fri Feb 28, 2020 4:25 pm
A negative delta G indicates a spontaneous reaction, and a positive delta G indicates a nonspontaneous reaction.

Re: Spontaneity

Posted: Fri Feb 28, 2020 4:42 pm
If you are observing a galvanic cell, you can also tell if a reaction is spontaneous if EĀ°cell is positive.

Re: Spontaneity

Posted: Fri Feb 28, 2020 4:57 pm
A reaction is spontaneous when $\Delta G< 0$. This is because there is available energy released by the reaction that can used to perform work. Remember that if the change in gibbs free energy of a forward reaction is positive, its reverse reaction can be spontaneous because the change in gibbs free energy of the reverse reaction would be negative. In addition, using the equation $\Delta G= -nFE$, you can conclude that if the cell potential (E) is positive, then the change in gibbs free energy is negative, allowing the reaction to be spontaneous.

Re: Spontaneity

Posted: Fri Feb 28, 2020 5:37 pm
A reaction is spontaneous if the delta G is negative, and it is non spontaneous when the delta G is positive. When talking about electrochemistry, a positive E cell means the reaction is spontaneous, and a negative E cell means the reaction is non spontaneous.

Re: Spontaneity

Posted: Fri Feb 28, 2020 7:46 pm
Spontaneous reactions can be detected by a negative Gibbs free energy and positive potential difference.

Re: Spontaneity

Posted: Fri Feb 28, 2020 7:58 pm
when delta G is negative it means the reaction is spontaneous

Re: Spontaneity

Posted: Fri Feb 28, 2020 10:21 pm
In addition to the sign of Gibbs free energy, the sign of cell potential can also serve as an indicator: if Ecell is greater than zero, the reaction is spontaneous, vice versa.

Re: Spontaneity

Posted: Fri Feb 28, 2020 11:12 pm
When you have a +E naught , it means that you will get a -deltaG , which means that k>1. A -deltaG is spontaneous.
When you have a -E naught, it means that you will get a +deltaG , which means that k<1. A +deltaG is non spontaneous.

Re: Spontaneity

Posted: Fri Feb 28, 2020 11:13 pm
positive cell potential (-E) = negative delta G = spontaneous
negative cell potential (+E) = positive delta G = nonspontaneous

Re: Spontaneity

Posted: Sun Mar 01, 2020 12:00 pm
The change is delta G needs to be negative

Re: Spontaneity

Posted: Sun Mar 01, 2020 1:29 pm
For the reaction to be spontaneous, delta G has to be negative