When 0.300 g of a diprotic acid was titrated with 0.100 M LiOH, 40.0 mL of the LiOH solution was needed to reach the second equivalence point. Identify the formula of the diprotic acid.

Question

Quizplus · Accepted Answer

First, we need to calculate the number of moles of LiOH used at the second equivalence point:
0.100 M LiOH x 0.0400 L LiOH = 0.00400 mol LiOH

Since LiOH is a strong base, it will react completely with both acidic protons of the diprotic acid. Therefore, the number of moles of the diprotic acid at the second equivalence point is equal to twice the number of moles of LiOH used:
2 x 0.00400 mol LiOH = 0.00800 mol diprotic acid

Now we can use the mass and number of moles of diprotic acid to calculate its molar mass:
0.300 g diprotic acid / 0.00800 mol diprotic acid = 37.5 g/mol

Looking at the answer choices, only option C has a diprotic acid with a molar mass close to 37.5 g/mol. The formula of the diprotic acid in option C is H2C2O4, also known as oxalic acid.

When 0300 G of a Diprotic Acid Was Titrated with 0