titrations part 1

Question

Potassium hydrogen phthalate is a solid, monoprotic acid frequently used in the laboratory as a primary standard. It has the unwieldy formula of KHC₈H₄O₄. This is often written in shorthand notation as KHP.

If 29.27 mL of a sodium hydroxide solution are needed to neutralize 3.427 grams of KHP, what is the concentration (mol/L) of the sodium hydroxide solution?

Answer 1

Let's begin by looking at the equation for the reaction between sodium hydroxide and KHP:

NaOH + KHC₈H₄O₄ ==> NaKC8H4O4 + H2O (note a 1:1 mole ration of NaOH:KHP)

Molar mass KHP = 204.2 g / mole

Moles KHP present = 3.427 g KHP x 1 mol / 204.2 g = 0.01678 moles KPH

Moles of NaOH needed to neutralize 0.01678 mols KHP = 0.01678 mols NaOH (1:1 mol ratio)

Concentration of NaOH = 0.01678 mol NaOH / 29.27 ml x 1000 ml / L = 0.5733 mol / L