Question

Suppose a 25.00 mL sample of a solution of a diprotic acid of unknown concentration requires 30.59 mL of a solution of 0.600MKOH to reach the end point. What is the molarity of the diprotic acid?

Answer 1

The molarity of the diprotic acid is 0.367 M.

Step-by-step explanation:

To find the molarity of the diprotic acid, we can use the equation:

H2A + 2KOH -> K2A + 2H2O

We know that 25.00 mL of the diprotic acid requires 30.59 mL of a 0.600 M solution of KOH to reach the end point. Based on the stoichiometry of the reaction, we can determine the number of moles of KOH used:

moles of KOH = 0.600 M x 0.03059 L = 0.018354 mol

Since the ratio of H2A to KOH is 1:2, the number of moles of H2A is:

moles of H2A = 0.018354 mol x 1/2 = 0.009177 mol

The molarity of the diprotic acid can be calculated by dividing the moles of H2A by the volume of the sample:

Molarity of H2A = 0.009177 mol / 0.02500 L = 0.367 M

Answer 2

To determine the molarity of the diprotic acid, the amount of titrant used (KOH) is first converted to moles and then related to the moles of acid based on the 2:1 mole ratio, yielding a molarity of 0.367 M for the unknown diprotic acid.

Step-by-step explanation:

To find the molarity of the diprotic acid, which requires 30.59 mL of a 0.600 M KOH solution to reach the equivalence point, we'll use the concept of titration. Since KOH is monovalent (providing one OH- per molecule) and the acid is diprotic (donating two H+ ions per molecule), the mole ratio is 2:1 with respect to KOH:acid.

The moles of KOH used in the titration can be calculated using the molarity and volume of the KOH solution.

Moles of KOH = Molarity of KOH × Volume of KOH (in liters)

Moles of KOH = 0.600 M × 0.03059 L = 0.018354 moles

Because the mole ratio is 2:1, the moles of diprotic acid will be half of the moles of KOH:

Moles of diprotic acid = 0.018354 moles ÷ 2 = 0.009177 moles

The molarity of the diprotic acid is then found by dividing the moles of acid by the volume of the acid solution in liters (25.00 mL is 0.025 L).

Molarity of diprotic acid = Moles of acid ÷ Volume of acid (in liters)

Molarity of diprotic acid = 0.009177 moles ÷ 0.025 L = 0.367 M