Question

To measure the amount of ascorbic acid (HC6H7O6, molar mass 176.13 g/mole) in a commercial brand of vitamin C tablets, a chemist titrated two tablets with 0.1500 M NaOH. 22.71 mL of the base were required to reach the equivalence point. How many milligrams of ascorbic acid were in each tablet?

HC6H7O6 + NaOH ---> Na + C6H7O6 + H2O

Answer 1

HC₆H₇O₆ + NaOH    Na⁺ + C₆H₇O₆^- + H₂O

In the above reaction,

1 mole of ascorbic acid (HC₆H₇O₆) produces 1 mole of C₆H₇O₆^-

We have to calculate first how many moles of OH^-were required.

0.02271 L x (0.1500 mole / L) = 0.00341 moles of OH^-

Since, there is a 1 : 1 relationship between ascorbic acid and NaOH, so there was 0.00341 moles of Ascorbic acid

Molar mass of Ascorbic acid = 176.13 g/mole

So, 1 mole of Ascorbic acid = 176.13 g

0.00341 moles of Ascorbic acid = (0.00341 x 176.13) g = 0.6 g

So, mass of each table = (0.6/2) g = 0.3 g = 300 mg