An analytical chemist weighs out 0.291 g of an unknown diprotic acid into a 250 mL volumetric flask and dilutes to the mark with distilled water. He then titrates this solution with 0.0800 M NaOH solution. When the titration reaches the equivalence point, the chemist finds he has added 61.6 mL of NaOH solution. Calculate the molar mass of the unknown acid. Round your answer to 3 significant digits
To solve this problem, we need to use the concept of stoichiometry and the relationship between the moles of acid and the volume of NaOH solution used.
1. Calculate the number of moles of NaOH used in the titration:
moles NaOH = volume NaOH (L) * concentration NaOH (mol/L)
moles NaOH = 0.0616 L * 0.0800 mol/L
moles NaOH = 0.004928 mol
2. Use the stoichiometric ratio between the unknown diprotic acid and NaOH to find the number of moles of acid used:
moles acid = 2 * moles NaOH = 2 * 0.004928 mol
moles acid = 0.009856 mol
3. Calculate the molar mass of the unknown acid:
molar mass = mass of acid (g) / moles acid
molar mass = 0.291 g / 0.009856 mol
molar mass = 29.52 g/mol
Rounding to three significant digits, the molar mass of the unknown acid is 29.5 g/mol.