The pH of hydrochloric acid is 0. This reading is taken from a solution of 1 mole of hydrochloric acid. A less concentrated solution of the acid, such as a 0.5-mole solution, has a higher pH, meaning it would be less acidic.
The pH of a solution measures the concentration of hydrogen ions it contains; the greater the number of hydrogen ions, the lower the pH. A strong acidic solution such as 1 mole of hydrochloric acid contains a high concentration of hydrogen ions. This means that the hydrogen and chlorine would have completely dissociated from each other, leaving no molecules of HCl in solution. The resulting solution would consist of only hydrogen ions and chlorine ions.