A solution’s pH value is the negative base-10 log of the solution’s hydronium ion concentration.
In Lab, solutions are generally 1 M or less in concentration. So, we get no more than 1M hydrogen ions where pH is 1, or at the other end no more than 1 M hydroxide ions corresponding to pH 14.
Since pH is a logarithmic measure, it is equal to a ten-fold change in hydrogen ion concentration for a difference of one pH unit.
