1. Improving Conductivity:
* Pure water is a poor conductor of electricity. This is because water itself doesn't readily dissociate into ions.
* When salt is added, it dissolves into its constituent ions: sodium ions (Na+) and chloride ions (Cl-).
* These ions increase the electrical conductivity of the water, allowing the electric current to flow more easily.
2. Facilitating the Reactions:
* At the anode (positive electrode): Chloride ions (Cl-) are attracted to the anode. They lose electrons and become chlorine gas (Cl2).
* At the cathode (negative electrode): Water molecules (H2O) are attracted to the cathode. They gain electrons and are reduced to hydrogen gas (H2) and hydroxide ions (OH-).
Without salt:
* The electrolysis of pure water would be very slow, if it happened at all.
* The reaction would primarily produce oxygen gas at the anode.
* Very little hydrogen gas would be produced, as the water molecules would be reluctant to accept electrons without the presence of a catalyst.
With salt:
* The presence of ions significantly speeds up the reactions.
* The reactions are more balanced, producing both hydrogen and oxygen gas.
* The addition of salt also prevents the buildup of hydrogen ions (H+) at the cathode, which could otherwise hinder the reaction.
Important Note:
* The salt used in the electrolysis of water needs to be non-reactive with the electrodes and the products. Sodium chloride (NaCl) is a common choice because it meets this requirement.
* However, it is crucial to use pure salt (without impurities like calcium or magnesium) to avoid contaminating the water.
In summary, salt acts as an electrolyte in the electrolysis of water, enabling the efficient flow of current and accelerating the reactions to produce hydrogen and oxygen gas.
