Question

Citric acid (C6H8O7) is a triprotic acid found naturally in lemon juice, and it is widely used as a flavoring in beverages. What is the molarity of citric acid in commercially available lemon juice if 24.68mL of 0.901 M NaOH is required in a titration to neutralize 25.00 mL of the juice? How many grams of citric acid are in 100 mL of the juice? the molar mass of citric acid is 192.12g/mol.

Answer 1

Citric acid (C6H8O7) is a triprotic acid = H3A

H3A + 3 NaOH -----------------------> Na3A + 3H2O

M1 = molarity of NaOH = 0.901 M

V1 = volume of NaOH = 25 mL

n1 = moles of NaOH = 3

M2 = molarity of H3A = ?

V2 = volume of H3A = 25 mL

n2 = moles of H3A = 1

M1 V1 / n1 = M2 V2 / n2

0.901 x 24.68 / 3 = M2 x 25.00 / 1

M2 = 0.296 M

molarity of citic acid = 0.296 M

volume = 100 mL

molar mass = 192.12 g/mol

molarity = (mass / molar mass ) x 1000 / V

0.296 = (mass / 192.12) x 1000 / 100

mass = 5.70 g

mass of citic acid = 5.70 g