Before we go through the different types of electrode potential, let us quickly recall the definition of electrode potential. If we take a piece of metal and place it in a solution of its ions, the metal will acquire either a positive or negative charge. Taking this into consideration, a certain or definite potential difference will develop between the metal and the solution. The potential difference that is generated is known as the electrode potential.
We will also look at some examples to understand the concept a little better. If we take copper and place it in a solution in the presence of Cu2+ ions, it acquires a positive charge with respect to the solution. A potential difference is set up between the copper plate and the solution. The potential difference, thus developed, is termed the electrode potential of copper.
Likewise, if we take a plate of zinc and place it in a solution containing Zn2+ ions, it will acquire a negative charge with respect to the solution. Now, a potential difference is also set up between the zinc plate and the solution. So, the potential difference is termed the electrode potential of zinc.
Also Read: Standard Electrode Potential
Having said that, we will now look at the different types of electrode potential.
Usually, we can notice two major changes whenever a metal rod is immersed in its salt solution. There will be oxidation and reduction.
When we talk about oxidation, during this process, the metal ions pass from the electrode into the solution. Excess electrons are left behind. As a result, a negative charge is acquired on the electrode. The tendency of the metal to change into ions is known as electrolytic solution pressure.
On the other hand, during reduction, metal ions in solution have a tendency to gain electrons from the electrode. So a positive charge is acquired on the electrode. Metal ions get accumulated on the metal surface, due to which the metal acquires a positive charge.
However, in both cases, a potential difference is set up.
Meanwhile, if we talk about the magnitude of the electrode potential of metal, in simple words, we can say that it is a measure of the relative tendency to undergo oxidation or reduction.
So, coming to the types of electrode potential, we can say that it solely depends on the nature of the metal electrode to lose or gain electrons. Thus, the electrode potential is of two main types: oxidation potential and reduction potential.
Oxidation Potential
When an electrode is negatively charged with respect to the solution, or if it acts as an anode, then oxidation occurs.
M → Mn+ + ne–
Reduction Potential
When the electrode is positively charged with respect to the solution, or if it acts as a cathode, reduction takes place.
Mn+ + ne– → M
Points to Remember
Here are some of the important points to remember.
- We cannot measure the absolute value of the single electrode potential directly.
- Experimentally, we can only measure the difference in potential between the two electrodes. In such as case, we will need to pair the electrode with another electrode with a known potential or, in other words, a “reference electrode”. Here, the EMF of the resulting cell is measured.
- The EMF of the cell is equal to the sum of potentials on the two electrodes. It can be given as
Emf of the cell = EAnode + ECathode = Oxidation potential of the anode + Reduction potential of the cathode
Types of Electrode Potential Video Lesson
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