An aqueous solution of copper sulfate is acidic in nature because the salt undergoes hydrolysis.

Hydrolysis is a chemical reaction where a compound reacts with water, resulting in the formation of new species. In the case of copper sulfate (CuSO4) dissolved in water, the water molecules can react with the ions present in the salt.

When copper sulfate dissolves in water, it dissociates into copper ions (Cu2+) and sulfate ions (SO4²?). The water molecules can hydrolyze the copper ions, leading to the formation of hydronium ions (H3O+) and copper hydroxide (Cu(OH)2).

Cu2+ + 2H2O -> Cu(OH)2 + 2H3O+

The formation of hydronium ions (H3O+) results in an increase in the concentration of H+ ions in the solution, making it acidic. Therefore, the aqueous solution of copper sulfate is acidic due to the hydrolysis of the salt.