The Nernst Equation calculator computes the cell electric potential (E) at 25 degrees C using the Nernst Equation (E = E0 – 0.0592/n • logQ).
INSTRUCTIONS: Choose the preferred units and enter the following:
Cell Electric Potential (E): The calculator returns the potential in volts. However, this can be automatically changed to other electrical potential units via the pull-down menu.
The Nernst Equation (at 25 degrees C)[1], E = E0 – 0.0592/n • logQ, calculates cell potential under non-standard conditions. Cell potential is a method of measuring the amount of voltage that exists between two half cells of a battery, and will be measured in Volts. This equation relates cell potential to the reaction quotient (Q = [products]y/[reactants]x) and provides an accurate method of measuring equilibrium constants.
The inputs are:
Substituting the above values into the Nernst Equation at 250 C will result in an electrode potential under nonstandard conditions. This equation is commonly used in electrochemistry and was even involved in the discovery of cold fusion.
The thermodynamic reaction quotient, Q, will most likely need to be calculated before entering it into this equation (unless it is explicitly given in a problem). In order to find Q, you could enter your data into the Reaction Quotient Equation in vCalc, or, you could follow the instructions below. To find Q, you first need to write the balanced chemical reaction:
Example:
aA + bB = dD + eE
Next, put the concentration of the products over the reactants, and solve for Q, as shown below:
Q= [products] / [reactants]
Q = [E]e [D]d / [B]b [A]a
Khan Academy: Cell Potentials Under Non-standard Conditions
Reaction Quotient (Q) (for the Spanish site click here)
Whitten, et al. "Chemistry" 10th Edition. Pp. 828
[1] For the Spanish site click here