An analytical chemist weighs out 0.132 g of an unknown triprotic acid into a 250 mL volumetric flask and dilutes to the mark with distilled water. He then titratws this soluteion with 0.1600 M NaOH solution. When the titration reaches the equivalence point, the chemist finds he has added 25.3 mL of NaOH solution. Calculate the molar mass of the unknown acid. Round your answer to 3 significant digits
First, we need to determine the number of moles of NaOH that reacted with the triprotic acid. We can use the equation:
Number of moles of NaOH = Molarity of NaOH × Volume of NaOH solution (in L)
Converting the volume of NaOH solution from mL to L:
25.3 mL = 0.0253 L
Number of moles of NaOH = 0.1600 M × 0.0253 L
= 0.004048 mol of NaOH
Since the triprotic acid is triprotic, it can react with 3 moles of NaOH for every mole of acid. Therefore, the number of moles of the unknown acid is also 0.004048 mol.
Now, we can calculate the molar mass of the unknown acid using the equation:
Molar mass = Mass of unknown acid / Number of moles of unknown acid
Mass of unknown acid = 0.132 g
Molar mass = 0.132 g / 0.004048 mol
= 32.612 g/mol
Rounded to three significant digits, the molar mass of the unknown acid is 32.6 g/mol.