The strength of an acid is always based on the concentration of hydrogen ions (H+). That is why acidity is measured by pH (power of hydrogen). PH is a negative log of the concentration of hydrogen ions in the solution.
Technically speaking, you could also say that the strength of an acid depends on the hydronium ion (H3O+) concentration. These are simply hydrogen ions dissolved in water:
H+ (aq) + H2O (l) ----- H3O+ (aq)
On the other hand, the strength of a base depends on the concentration of hydroxyl (OH-) ions.
A pH below 7 indicates that a solution is acidic, a pH of 7 says it is neutral and a pH above 7 is for alkaline solutions.
Technically speaking, you could also say that the strength of an acid depends on the hydronium ion (H3O+) concentration. These are simply hydrogen ions dissolved in water:
H+ (aq) + H2O (l) ----- H3O+ (aq)
On the other hand, the strength of a base depends on the concentration of hydroxyl (OH-) ions.
A pH below 7 indicates that a solution is acidic, a pH of 7 says it is neutral and a pH above 7 is for alkaline solutions.