Question

A solution tested with a pH indicator shows that the pH is 9. What is the H+ (hydrogen ion) concentration of the solution?

Answer 1

pH is the negative log of the hydrogen concentration. The letter p literally means a negative log.

pH = - log [H+]

         or

[H+] = 10-pH

Here PH is 9 so [H+] = 10-9

Hydrogen-ion concentration of a solution with a pH of 9 is 10-9mol/l,

meaning it contains 0.000000001 mol of hydrogen ions in a solution of 1 liter.