Attachment data exported to attachments-and-meta.csv. MCAT Chemistry Question — Nernst Equation | Next Step Test Prep
Return to MCAT® Blog Homepage

MCAT Chemistry Question — Nernst Equation

The voltage of a galvanic cell, E, depends on the concentration of reactants and products. The Nernst equation,

E = Eo – (0.0592/n)log(Q)

can be used to calculate the cell potential. Eo is the standard cell potential, n is the number of moles of electrons exchanged in the reaction, and Q is the reaction quotient. Which of the following is true regarding the value of E?


A. E is always less than Eo

B. E is always greater than Eo

C. E is always equal to Eo

D. E can be less than, greater than, or equal to Eo

Click for Explanation

According to the Nernst equation, the cell potential E will vary based on the logarithm of the reactant quotient Q. The reactant quotient follows the same equation as the equilibrium constant K, but measures the ratio of the actual concentration of products to concentration of reactants at any time during the reaction. Therefore, when Q > 1, log(Q) is positive and E < Eo. If Q < 1, log(Q) is negative, then E > Eo. Lastly, E is equal to Eo when Q = 1 because the log of one is equal to zero. Thus, E can be less than, greater than, or equal to Eo making D the correct answer.

Want more MCAT practice?

We’ve got options for every schedule and learning style!

From the best online MCAT course created by top instructors with 524+ MCAT scores to the most representative full-length practice exams and private tutoring, we can custom tailor your MCAT prep to your goals!

Not sure which option is right for you? Schedule a free MCAT consultation with an MCAT expert using the form below. No obligation, just expert advice.

Create your Free Account to access our MCAT Flashcards SIGN UP NOW
MCAT is a registered trademark of the Association of American Medical Colleges (AAMC), which is not affiliated with Blueprint.