Reducing Agent: Definition & Examples

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  • 0:05 Agents of Reduction
  • 0:59 What is Actually Being…
  • 1:43 Redox Chemistry
  • 4:13 Why is Redox Chemistry…
  • 5:08 Lesson Summary
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Lesson Transcript
Instructor: Michael Williams
What is a reducing agent, and what does it do? Watch this video to find out. We'll also explore a couple of examples of everyday reactions that involve reducing agents.

Agents of Reduction

The online version of the Miriam-Webster dictionary defines an agent as a 'person or thing that causes something to happen.' We often encounter agents in everyday life. For example insurance agents, sports agents, travel agents, housing agents, FBI agents, 007 agents, and the list goes on. Each of these individuals perform an essential role in allowing something to happen. Whether that's obtaining car insurance, getting the best endorsements and contracts for professional athletes or getting the dirt on the bad guys, the agent enables, or causes, these things to happen.

In chemistry, a reducing agent is an individual reactant in a reduction/oxidation (redox) reaction that reduces another reactant by donating electrons to that reactant. If a reducing agent isn't present to pass along electrons to the other substance, reduction cannot occur and the redox reaction is halted.

What is Actually Being Reduced?

We just read that the reducing agent gives up, or donates, electrons to the other reactant, which might make it seem like the reducing agent was, itself, reduced. After all, it is losing electrons. And, if the other reactant gains electrons, why do we say that it is reduced, didn't it just gain electrons?

This is where redox chemistry might seem a bit confusing until we realize what it is that is really being reduced. What is actually being reduced is a property known as the oxidation state, which is representative of the overall, hypothetical charge of an atom. Remember that electrons carry a negative charge. So, when electrons are passed from one atom to another, the oxidation state of the atom that gains electrons is reduced.

Redox Chemistry

So, what is redox chemistry, and what is a redox reaction?

Redox chemistry can generally be defined as chemical reactions involving electron exchange between atomic species, which changes their respective oxidation states. When an atom loses electrons, its oxidation state increases, and we say that it is oxidized. When an atom gains electrons, it's oxidation state decreases, and we say that it is reduced.

A redox reaction consists of two halves, one for the reducing agent and another for the oxidizing agent. The reducing agent reduces the oxidizing agent and is, itself, oxidized (by the oxidizing agent) in the process. It is just the opposite for an oxidizing agent.

Here is an example equation:

CuO + Mg = Cu + MgO

In this equation, copper (II) Oxide reacts with magnesium metal to produce solid copper metal and magnesium (II) oxide.

To see the half reactions we need to understand that both oxides are ionic, but the metals are not.

First, we'll write the half reaction for Copper, which is:

Cu^(2+) + O^(2-) = Cu

And for magnesium, which is:

Mg = Mg^(2+) + O^(2-)

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