Increase in hydrogen ion occurs when the pH of an aqueous solution changes from 4 to 3.
The pH of an aqueous solution changes from 4 to 3 when the hydrogen ion concentration in the solution is increased because hydrogen ions in the solution is related to acidic nature of that solution while on the other hand, hydroxyl ions are related to alkaline nature of the solution.
So we can conclude that increase in hydrogen ion occurs when the pH of an aqueous solution changes from 4 to 3.
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