Acids: Produce an excess of hydrogen ions (\(H^{+}\)) when they dissolve in water

Alkalis/bases: Produce an excess of hydroxide ions(\(OH^{-}\)) when they dissolve in water

High concentration of hydrogen ions leads to a lower pH and a more acidic solution.

High concentration of hydroxide ions leads to a higher pH and a more basic solution.

If the concentration of hydrogen ions is increased by 10, the pH decreases by 1.

If the concentration of hydrogen ions is decreased by 10, the pH increases by 1.

If a strong and a weak acid are present in equal concentrations, then the strong acid will have a higher pH because it is more dissociated and hence has a higher concentration of hydrogen ions.