Why is a small amount of solute added in the electrolysis of water?
What solute? If it is an electrolyte (such as NaCl) it is done probably to increase the conductivity of the water.
In the electrolysis of water, a small amount of solute is often added to enhance the process. This is because pure water is a poor conductor of electricity due to its low concentration of ions. When a solute, such as an electrolyte or salt, is added to water, it increases the concentration of ions, making the water more conductive and facilitating the electrolysis process.
To understand this concept, it's important to have a basic knowledge of electrolysis. Electrolysis is a process that uses an electric current to drive a non-spontaneous chemical reaction. In the case of water electrolysis, the goal is to split water molecules (H2O) into its constituent elements, hydrogen (H2) and oxygen (O2).
To carry out the electrolysis of water, you need an electrolytic cell with two electrodes: a cathode (negative electrode) and an anode (positive electrode). When an electric current is applied across the electrodes, certain chemical reactions occur at each electrode.
At the cathode, hydrogen gas (H2) is produced by the reduction of water molecules:
2H2O (l) + 2e- → H2 (g) + 2OH- (aq)
At the anode, oxygen gas (O2) is produced by the oxidation of water molecules:
2H2O (l) → O2 (g) + 4H+ (aq) + 4e-
Now, the reason for adding a small amount of solute (usually an electrolyte or salt) is to increase the conductivity of the water. Conductivity is a measure of how well a substance can conduct an electric current. Pure water has a low conductivity because it has a very low concentration of ions. Ions are charged particles that facilitate the flow of electricity through a solution.
By adding a solute, the concentration of ions in the water is increased. This results in the generation of more ions in the solution, making it a better conductor of electricity. As a result, the electrolysis process becomes more efficient and proceeds at a faster rate.
However, it's essential to note that only a small amount of solute is added because adding too much can lead to undesirable side reactions or complications in the electrolysis process. The added solute should not participate in the electrochemical reactions; its primary purpose is to enhance the conductivity of the water.
So, to summarize, a small amount of solute is added in the electrolysis of water to increase the concentration of ions in the solution, which improves its conductivity and facilitates the electrolysis process, resulting in the production of hydrogen and oxygen gases at the respective electrodes.