Potassium hydrogen phthalate is often used to standardize solutions of strong bases. Highly pure samples of this solid weak acid are readily available. It is stable and easy to use in the laboratory. Calculate the molarity of a sodium hydroxide solution if 23.73 mL are required to titrate 0.5816 g of potassium hydrogen phthalate (C8H5O4K).

0.12 M

Explanation:

Molarity of sodium hydroxide = number of moles of sodium hydroxide / volume in liters

equation of reaction between NaOH and Potassium hydrogen phthalate

NaOH(aq) + KHC₈H₄O₄(aq)  KNaC₈H₄O₄(aq) + H₂O(aq)

molar mass of KHC₈H₄O₄ = 204.22g/mol

amount required to titrate with NaOH = 0.5816 g

mole of  KHC₈H₄O₄ = 0.5816 g / 204.22g/mol = 0.00285 mole

considering the equation, 1 mole of NaOH required 1 mole of KHC₈H₄O₄

0.00285 mole  KHC₈H₄O₄ will require 0.00285 mole of NaOH

Molarity = 0.00285 mole  / ( 23.73 ml / 1000ml) L = 0.12 M