Question

An unknown liquid carboxylic acid (60 mg) with two oxygen atoms in the molecule is titrated with 0.050 M sodium hydroxide solution. The phenolphthalein endpoint was reached when 20.2 mL of the base had been added. Calculate the molecular weight of the acid and find its formula.

Answer 1

concentration of NaOH = 0.050 M

volume = 20.2 mL

moles of NaOH = 0.050 x 20.2 / 1000

                       = 1.01 x 10^-3

moles of NaoH = moles of an acid

moles of acid = 1.01 x 10^-3

moles = mass / moalr mass

1.01 x 10^-3 = 60 x 10^-3 / Molar mass

Molar mass of an acid = 59.4 g/mol