Here's why:

* The pH scale: The pH scale measures the acidity or alkalinity of a solution. It ranges from 0 to 14.

* Acidity: Lower pH values indicate higher acidity.

* Neutrality: A pH of 7 is neutral.

* Alkalinity: Higher pH values indicate alkalinity (basicity).

So, pH 2 is the most acidic, followed by 5, then 7, and finally 11, which is the most alkaline.