What is the relationship between equilibrium constant and delta G?

DeltaG tells us whether a reaction is spontaneous or not. If delta G is negative, the reaction is spontaneous, and if delta G is positive, the reaction is not spontaneous. There is a relationship between deltaG and equilibrium constant, K. It is given by the formula deltaG=-RTlnK, where R is the gas constant (8.314J K−1 mol−1), T is the temperature in Kelvin, and K is the equilibrium constant.

Can we figure out if the reaction is spontaneous or not just from equilibrium constant K? Yes!

If we plug in ln of a number less than zero on our calculator, we will get a negative number. This, in turn, will turn delta G into a positive number and therefore when k<0, deltaG>0, and the reaction is non spontaneous.

For values of k above 1, delta G is less than zero, making the reaction spontaneous. For k=1, lnk=0, making delta G=0.

Note: If a reaction is spontaneous in one direction, it will be non spontaneous in the opposite direction and vice versa.

Some other important formulas for deltaG are:

deltaG = deltaH-TdeltaS, where deltaH is enthalpy and delta S is change in entropy, and T is the temperature in Kelvin. Note that enthalpy or entropy alone does not tell us whether a reaction is spontaneous or not. It is delta G that we need to use to figure out the spontaneity of the reaction.

For more help with your chemistry classes, please call Transformation Tutoring at 646-407-9078 to talk to our incredible chemistry tutors in NYC, Brooklyn and online.



Recent Posts

See All

Live Online Chemistry Classes

Transformation Tutoring is happy to offer live online group chemistry classes for the 2020-2021 school year. Classes are : Honors SAT Subject Chemistry and Introduction to Organic Chemistry. Classes w