Question

A student is given a solution containing 1.08 g of an unknown diprotic acid, H, A. To determine the molar

mass of the acid, the student titrates the sample using a 0.524 M solution of KOH(aq). The balanced
equation for the reaction is shown below.
H2A(aq) + 2 KOH(aq) - 2H2O(1) + K2A(aq)
1 35.5 mL of KOH(aq) are required to consume the acid completely, what is the molar mass of the
unknown acid?

Answer 1

To determine the molar mass of the unknown acid, we can use the stoichiometry of the reaction and the amount of KOH required to titrate the acid. The molar mass of the unknown acid is 3050.16 g/mol.

Step-by-step explanation:

To determine the molar mass of the unknown acid, we can use the stoichiometry of the reaction and the amount of KOH required to titrate the acid. According to the balanced equation, 1 mole of H2A reacts with 2 moles of KOH to form 2 moles of H2O and 1 mole of K2A. Since 1.35 mL of 0.524 M KOH is required to titrate the acid completely, we can calculate the number of moles of KOH used:

Moles of KOH = (0.00135 L)(0.524 mol/L) = 0.0007074 mol KOH

Using the molar ratio from the balanced equation, we can determine the number of moles of H2A:

Moles of H2A = (0.0007074 mol KOH)(1 mol H2A/2 mol KOH) = 0.0003537 mol H2A

Next, we can calculate the molar mass of the unknown acid:

Molar mass of H2A = (1.08 g)/(0.0003537 mol) = 3050.16 g/mol