Question

What makes a reaction reversible?

Answer 1

Hint:A reversible reaction means when the reactant turns into products and the products return back to the reactant and both the reactions are equilibrium. The factors that can make the reaction reversible can be heat or enthalpy, entropy, etc.

Complete step-by-step answer:We know that there are two types of reactions, i.e., reversible reaction and irreversible reaction. Reversible reactions are those, in which two reactions are in equilibrium, i.e., the reactants are being converted into a product and the products are again converting into reactants. While irreversible reactions are those, in which only the reactants are converting into products.
Suppose a reaction in which A and B are reactants, C and D are the products. The irreversible reaction is shown as:
$A+B\to C+D$
And the reversible reaction is shown as:
$A+B\rightleftharpoons C+D$
In nature, most of the reactions are irreversible but a little of them are reversible, and the factors that cause can be enthalpy or heat.
Suppose a reaction is spontaneous, i.e., the reaction takes place without any external efforts with the evolution of heat when the products are formed. But if we decrease the temperature of the reaction, then the products will start to convert back into reactants and will come into equilibrium.
For example, when the hydrogen and oxygen combine to water, and when the water is subjected to electricity it again dissociated into hydrogen and water, therefore, the external factor is electricity that made the reaction reversible.
Therefore, under some conditions their reactions are reversible.

Note: Some examples of reactions that can never be reversed are rusting of iron: once the iron is rusted it can never be used, boiling of an egg, formation of curd from the milk, etc.