A Method for a Titration

Next, using the weigh-by-difference method, measure a sample of potassium hydrogen phthalate, KHP (1) into a clean, dry 125-mL Erlenmeyer flask and dissolve it in 40 mL of water. KHP (MWT = 204.22 g/mol) is a monobasic acid that contains one mole of neutralizable hydrogen per mole of compound. Therefore, this monobasic acid reacts 1:1 stoichiometrically with sodium hydroxide, Equation 1.

To determine the mass of KHP required for the titration, you should first determine the number of moles of NaOH in approximately 15 mL of your titrant. Let’s say that your NaOH titrant concentration is 5.00 M. How many moles of NaOH would be present in 15.0 mL?

5.00 moles/L X 0.0150 L= 7.50 X10^-2 moles of NaOH.

Since sodium hydroxide reacts 1:1 with the KHP acid this also the number of moles of KHP needed for a complete reaction and neutralization. The grams required can be obtained by multiplying the moles of NaOH by the molecular weight of KHP.

7.50 X 10^-2 moles X 204.22 g KHP/ 1 mole = 15.3 g KHP