Question

A student is given a solution containing 0. 932 g of an unknown acid, H2A(aq) To determine the molar mass of the acid, the student titrates the sample using a 0. 481 M solution of KOH(aq).

1. Write the balanced equation for the reaction taking place. Include states of matter.


2. If 28. 9 mL of KOH is required to consume the acid completely, calculate the moles of H2A.


3. Calculate the molar mass of H2A.

Answer 1

1. The balanced equation for the reaction taking place between the unknown acid, H2A(aq), and KOH(aq) can be written as:

H2A(aq) + 2KOH(aq) → 2H2O(l) + K2A(aq)

2. To calculate the moles of H2A, we first need to determine the amount of KOH reacted. Given that 28.9 mL of 0.481 M KOH solution is required to consume the acid completely, we can calculate the moles of KOH:

Moles of KOH = Volume (L) × Concentration (M)
= 0.0289 L × 0.481 mol/L

Next, since the balanced equation shows that 1 mole of H2A reacts with 2 moles of KOH, the moles of H2A can be calculated:

Moles of H2A = (Moles of KOH) / 2

3. To calculate the molar mass of H2A, we need to know the moles of H2A and the mass of the sample. Given that the sample contains 0.932 g of the unknown acid, we can calculate the molar mass:

Molar mass of H2A = Mass (g) / Moles of H2A

By substituting the values into the equation, we can determine the molar mass of H2A.