Question

Explain which type of change occurs when water is electrolyzed?
(This question has multiple correct options.)
(A) Reversible
(B) Irreversible
(C) Physical
(D) Chemical

Answer 1

Hint: In the electrolysis of water, external electric current is given to water in which water gives hydrogen and oxygen gases at the electrodes. The products in this reaction are not in equilibrium with the reactants.


Complete step by step solution:
Let’s see what occurs in the electrolysis of water.
- The electrolysis of water is an electrolytic method by which we can convert water to a mixture of hydrogen and oxygen gas. This process can be described in the form of reaction as below.
\[2{{H}_{2}}{{O}_{(l)}}\to 2{{H}_{2(g)}}+{{O}_{2(g)}}\]
- A reversible change is a change in which products are in equilibrium with the reactants and so we can also obtain reactants from the product molecules.
- An irreversible change is the one in which products cannot give the reactants back. So, the products and the reactants are not in equilibrium.
- Here, the reaction is not in equilibrium and we cannot get water from the reaction between hydrogen and oxygen gas. So, this change is an irreversible change.
- Now, physical change is a change in which physical state of the compound or colour is changed. Here, we can say the water is in a liquid state and hydrogen and oxygen are in a gaseous state. So, a change in a physical state is there in the reaction. Therefore we can say that a physical change is involved in the reaction.
- If new compounds are synthesized from a particular compound, then a chemical change is there. Here, hydrogen gas and oxygen gas is produced from water. So, a chemical change is also involved in this reaction.

- So, we can conclude that options (B), (C) and (D) are correct.


Note: Remember that in order to consider that a chemical change has occurred, it is necessary that the molecular formula of products is different from the reactant molecules. Note the hydrogen and oxygen gas can combine to give water in presence of suitable catalysts and at high pressure but this kind of conditions are not present in the electrochemical cell. So, the change cannot be reversible.