Electrochemical Cell

An electrochemical cell uses chemistry to produce electricity.

Electrochemical Cell: A Battery!!

To learn about electrochemical cells, we are going to look at a redox reaction that can produce electricity.

Our example problem will be a reaction between silver and aluminum.

Reduction Half Reactions

Let’s look up the reduction half reactions:

Ag+ + 1e- Ag Eo = +0.799 volts

Al+3 + 3e- Al Eo = -1.66 volts

Since both of these are reduction half reactions, we must determine which of them is oxidized.

Which one is oxidized?

Ag+ + 1e- Ag Eo = +0.799 volts

Al+3 + 3e- Al Eo = -1.66 volts

To show oxidation, we will reverse one of the reactions. Which one? Keep in mind:

#1 – When you reverse a ½ reaction, the sign changes on electrode potential. (Eo)

#2 – You want to end up with the sum of the electrode potential to be positive.

Let’s oxidize the Aluminum!!

Ag+ + 1e- Ag Eo = +0.799 volts

Al+3 + 3e- Al Eo = -1.66 volts

If you oxidize the aluminum, the half reaction looks like this:

Al Al+3 + 3e- Eo = +1.66 volts

What does that look like?

Aluminum losing electrons

The aluminum is losing electrons and they go to the DMM to record the voltage.

Silver is gaining electrons

The piece of silver will gain the electrons and then the pieces of copper complete the circuit.

Two half cells

The silver electrode is The aluminum electrode

gaining electrons so it is losing electrons so it

is called the cathode. is called the anode.

Putting it all together!!

Ag+ + 1e- Ag Eo = +0.799 volts

Al Al+3 + 3e- Eo = +1.66 volts

Eo = +2.459 volts

So what is really going on?

The piece of aluminum is losing electrons and breaking apart into Al+3 ions that fall into the solution.

The piece of silver is gaining electrons and the Ag+ ions in the solution are attracting to the silver metal.

In the end……

Eventually, the chemicals will run out and the battery will not produce anymore electricity.

Wet Cell

The battery (electrochemical cell) described in this presentation is commonly called a DRY cell battery.

Another type of battery is a wet cell battery, typically used as car batteries. They are also called lead acid batteries because they use the metal lead with sulfuric acid to produce electricity.

Two Types of Batteries

Dry cell batteries, sometimes called alkaline batteries because their solutions are basic.

Wet cell batteries, sometimes called lead acid batteries.