What is PH

Aug 26, 2022, 16:45 IST

About PH

Many properties of aqueous solutions depend on the concentration of H+ ions of the solutions and therefore there is a need to express these concentrations in simple terms. For this purpose we introduce the concept of pH. 

pH  = – log aH+ (where aH+ is the activity of H+ ions).

Activity of H+ ions is the concentration of free H+ ions in a solution. By free, we mean those that are at a large distance from the other ion so as not to experience its pull. We can infer from this that in dilute solutions, the activity of an ion is same as its molar concentration since more number of solvent molecules would separate the two ions. For concentrated solutions the activity would be much less than the concentration itself. Therefore, the earlier given expression of pH can be modified for dilute solutions as, pH = – log [H+]. This assumption can only be made when the solution is very much dilute, i.e., [H+]  1M. For higher concentration of H+ ions, one needs to calculate the activity experimentally and then calculate the pH.

Find below details about PH calculations