Determining the Molarity of Phosphoric Acid in a Titration Experiment

How can we calculate the molarity of phosphoric acid in a titration experiment?

Given the titration curve of 13 mL phosphoric acid with 0.102 M KOH, what is the molarity of the phosphoric acid?

Calculating the Molarity of Phosphoric Acid

The molarity of the phosphoric acid in the given titration example is approximately 0.034 M. This is calculated by first determining the moles of KOH used and then deducing the moles of the triprotic phosphoric acid. The molarity is then found by dividing the moles of acid by the sample volume.

In order to calculate the molarity of phosphoric acid in a titration experiment, we need to first determine the moles of the substances involved. In this specific example with 13 mL of phosphoric acid and 0.102 M KOH, the process involves finding the moles of KOH used and then relating it to the triprotic nature of phosphoric acid.

Given that 0.102 M KOH was used and the volume is 0.013 L (converted from 13 mL), the moles of KOH can be calculated as follows: Moles of KOH = Molarity × Volume = 0.102 mol/L × 0.013 L = 0.001326 mol

As phosphoric acid is a triprotic acid and KOH is a strong base, each molecule of KOH neutralizes three moles of H+ from phosphoric acid. Therefore, the moles of phosphoric acid in the original sample can be deduced by dividing the moles of KOH by 3: Moles of phosphoric acid = 0.001326 mol / 3 = 0.00044189 mol

Finally, the molarity (concentration) of the phosphoric acid in the solution is determined by dividing the moles of phosphoric acid by the volume in liters: Molarity = Moles of phosphoric acid / Volume = 0.00044189 mol / 0.013 L = 0.03399 M or approximately 0.034 M

By following this calculation method, the molarity of phosphoric acid in the titration experiment can be accurately determined, providing valuable insight into the concentration of the acid solution used.