Return to MCAT® Blog Homepage

MCAT Chemistry Question — Strongest Reducing Agent

Given the list of reduction potentials, which of the following species is the strongest reducing agent?

 

Li+(aq)+ e–  →Li (s) Eored = -3.04 V

Zn2+(aq) + 2 e→ Zn (s) Eored = -0.76 V

Ag+(aq)  + e→ Ag (s) Eored = 0.80 V

Ce4+(aq)  + e→ Ce3+ (s) Eored = 1.44 V

 

A. Ce4+

B. Zn2+

C. Li

D. Ag

 

Explanation

 

This question is testing your understanding of the redox chemistry and reduction potentials. To answer this question, you must first know that a reducing agent is itself oxidized. Therefore, the strongest reducing agent is going to be the species that is most readily oxidized. The Nernst equation, DG = -nFE, shows that a spontaneous reaction (DG < 0) corresponds to an electrochemical potential, E, that is greater than zero.

 

Since Ce4+ is spontaneously reduced, choice A can be eliminated. Zn2+ is already in its oxidized form and therefore cannot be oxidized further making B the wrong answer. Considering answer choices C and D, you must reverse the reactions to find Eoox, which equals the negative of the reduction potential (Eoox = -Eored). Therefore, the oxidation of Ag(s) is a nonspontaneous reaction while the oxidation of Li(s) proceeds spontaneous with a potential of +3.04 V, making C 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 Advisor using the form below. No obligation, just expert advice.

Schedule My Free Consultation

MCAT is a registered trademark of the Association of American Medical Colleges (AAMC), which is not affiliated with Blueprint.