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One proton or hydrogen atom per molecule is a monoprotic acid provided to an aqueous solution. Before releasing its proton, a monoprotic acid's electrical charge increases by one level. Any acid with only one hydrogen atom in its formula is called a monoprotic acid, while some acids with multiple hydrogen atoms may also fall under this category. In other words, while all monoprotic acids contain only one hydrogen, not all single-hydrogen acids are monoprotic.

Example: Acetic acid.

The titration curve of monoprotic acid has a start, middle, and end point. At the starting point, pure acetic acid is found. When you can start the titration, at the middle point both${\mathrm{H}}^{+}$and${\mathrm{CH}}_3{\mathrm{COO}}^{-}$are in equal amounts. At the last or endpoint, only${\mathrm{CH}}_3{\mathrm{COO}}^{-}$ion is obtained.

The polyprotic acids, are acids that can donate more than one proton or hydrogen. The ability to give several protons allows polyprotic acids to be further divided into groups called diprotic, triprotic, and so on. Each ionization step's pKa value is different for a polyprotic acid, and two equivalence points are obtained.

Example: ${\mathrm{H}}_2{\mathrm{SO}}_4$

The curves are displaced vertically along the pH axis but have comparable characteristics. At this time,$\left[\mathrm{HA}\right]=\left[\mathrm{A}-\right]$because the pH at the halfway point of each titration is numerically identical to the pK of its corresponding acid. Each titration curve has a substantially steeper slope towards its wings than near its midway. This shows that the pH of the solution is generally insensitive to the addition of either a strong base or a strong acid when$\left[\mathrm{HA}\right]=\left[\mathrm{A}-\right]$