Oxidation and Reduction Reactions for the MCAT: Everything You Need to Know
/Learn key MCAT concepts about oxidation and reduction reactions, plus practice questions and answers
(Note: This guide is part of our MCAT General Chemistry series.)
Table of Contents
Part 1: Introduction to oxidation and reduction reactions
Part 2: Overview of atomic structure
Part 3: Oxidation and reduction
a) Definitions
b) Assigning oxidation states
c) Hydrides
Part 4: Applications of redox reactions
a) Writing and balancing redox reactions
b) Electrochemical cells
c) Electron transport chain
Part 5: High-yield terms
Part 6: Passage-based questions
Part 7: Standalone practice questions
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Part 1: Introduction to oxidation and reduction reactions
Redox reactions constitute fundamental processes in our daily lives. Consider combustion, which creates fire and heat from oxygen gas and hydrocarbon fuel. Oxidation and reduction reactions are also key in creating energy from the food we eat. Additionally, these processes are key to the operations behind batteries, in which reduction and oxidation reactions generate the power we need to drive our cars.
Redox reactions refer to chemical reactions in which the exchange of electrons results in the oxidation of some atoms and the reduction of others. Success on this topic requires a detailed understanding of both oxidation and reduction and how oxidation states change over the course of a given reaction.
In this guide, we’ll start to break down the essentials of oxidation and reduction reactions needed to know for the MCAT. Throughout this guide, you will see several important words defined in bold. At the end of this guide, there are also several AAMC-style practice questions for you to test your knowledge against.
Let’s begin!
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Part 2: Overview of atomic structure
How are electrons spatially distributed in an atom? The electron cloud model provides us with an answer and proves to be useful in visualizing how electrons are lost (oxidation) and gained (reduction) in redox reactions.
The electron cloud model, developed by Erwin Schrödinger in the 1920s, describes electrons as being distributed within certain regions of probability around the central nucleus. The electron cloud model—which is the preferred model of modern scientists—is distinct from Bohr’s atomic model in which electrons were imagined to move in discrete concentric orbits around the nucleus—much like satellites around the Earth or the cabins of a Ferris wheel.
The electron cloud model emphasizes the indistinct nature of electron distribution. The electron cloud model theorized that electrons do not move in static orbits around the central nucleus, such that electrons are always a specific and discrete distance away from the center of the atom. Instead, we can only guess where an electron might be—that guess is mathematically computed and described as a region of probability called the electron cloud. These regions of probability can be visualized and illustrated as certain shapes, which gives rise to the atomic theory of subshells and electron orbitals.
For more information on atoms and how they behave, be sure to refer to our guide on atomic and nuclear physics.
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