MCAT Chemistry Question — Spontaneous Reaction
- Jun 18, 2014
- MCAT Question of the Day
What species is oxidized and what is the oxidizing agent in the following spontaneous reaction?
2Au3+(aq) + 3Cu (s) → 2Au (s) +3Cu2+ (aq)
A) Au3+, Au
B) Cu, Cu2+
C) Au3+, Cu
D) Cu, Au3+
For the MCAT, remember: oxidation is loss of electrons (OIL) and reduction is gain of electrons (RIG). The compound containing the element that is reduced is the oxidizing agent, and the compound containing the element that is oxidized is the reducing agent.
In this reaction, Cu (s) is oxidized because it loses 2 e–. Au3+ is the oxidizing agent because, although monatomic, it is the element in the compound that is reduced.
A) Au3+(aq), Au (s), incorrect, Au3+ (aq) is reduced to Au (s), and Au (s) is a product.
B) Cu (s), Cu2+ (aq), incorrect, Cu(s) is oxidized, and therefore the compound containing Cu (s) is the reducing agent. Note that although Cu (s) is the reducing agent in this reaction, the entire compound would be the reducing agent if the Cu were in a polyatomic molecule.
C) Au3+ (aq), Cu (s), incorrect, Au3+ (aq) is reduced, and Cu (s) is oxidized.
D) Cu (s), Au3+ (aq), correct.
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.
Search the Blog
Free ConsultationSchedule Now
MCAT Blog How to Review MCAT Full-Lengths
Free MCAT Practice AccountNeed great MCAT practice?
Get the most representative MCAT practice possible when you sign up for our free MCAT Account, which includes a half-length diagnostic exam and one of our full-length MCAT practice exams.Learn More