Identifying Redox Reactions — Overview & Examples

Features of a Redox Reaction

When determining if the reaction is a redox reaction it is important to identify:

• reduced species (gains electrons)

• oxidized species (loses electrons)

A redox reaction will always have something reduced and something oxidized. Usually redox reactions contain one or more of the following:

• Neutral diatomic molecules ($O_2$, $H_2$, $Cl_2$, $etc.$)

• Transition metals ($Fe, Cu, Ag, Pd, etc.$)

Look Out for Oxidation State Changes

The change in oxidation states, or oxidation numbers, from reactants to products will help distinguish the reduced and oxidized species.

Neutral diatomic molecules when borken, often experience a gain or loss of electrons. For example, $O_2$ is neutral, but $O^2$$^-$ has a $2-$ oxidation state.

Transition metals have various oxidation states which make them great for redox reactions. For example iron, $Fe$, can access oxidation states between $-2$ to $+7$. The most common oxidation states of iron is $+2$ and $+3$. To determine the oxidation state look at the atoms bound to $Fe$ in compounds. For example in $FeCl_3$, $Cl$ has a $-1$ oxidation state and there are 3 $Cl^-$s giving a $3-$ negative charge overall. To make a neutral compound Fe must be $+3$, $Fe^I$$^I$$^I$. Another example is $FeO$, where we have $O^2$$^-$ and $Fe^I$$^I$.

Checking Changes in Oxidation States

Iron has been used for thousands of years as a metal for things such as screws, bolts, tools, cookware, and more. These iron items can rust in the presence of oxygen in the air. Rust is the brown-orange layer that can form on the silvery iron. The balanced chemical reaction for this process is: $$4\ Fe\ (s)\ +\ 3\ O_2\ (g)\ \rightarrow\ 2\ Fe_2O_3\ (s)$$ The next steps is to check the oxidation states for each atom in the reactants and products: $$Oxidation\ States\\ Fe:\ 0\ \rightarrow\ +3\\ O:\ 0\ \rightarrow\ 2-\\$$ Both $Fe$ and $O$ start at a zero oxidation state in the reactants, but change in the products. $Fe$ loses electrons and becomes more positive while $O$ gains electrons and becomes more negative. $Fe$ is oxidized and $O_2$ is reduced.

(Video) Oxidation vs. Reduction, What are Oxidation and Reduction Reactions in Everyday Life?

by My Book of Chemistry

In this video, My Book of Chemistry shows you real-life examples of redox reactions. You'll learn four unique examples. This is a fun video for learning more about redox!