Question

A 0.25-mol sample of a weak acid with an unknown pKa was combined with 12.0 mL of 2.90 M KOH, and the resulting solution was diluted to 1.500 L. The measured pH of the solution was 3.95. What will the pH of the solution be if an additional 12.00 mL of 2.90 M KOH are added?

Answer 1

To calculate the pH of the solution after adding an additional 12.00 mL of 2.90 M KOH, we need to use the initial information. The initial solution contained a 0.25-mol sample of a weak acid, and the resulting solution was diluted to 1.500 L. The measured pH of the solution was 3.95.

Step-by-step explanation:

To calculate the pH of a solution after adding an additional 12.00 mL of 2.90 M KOH, we need to use the initial information. The initial solution contained a 0.25-mol sample of a weak acid, and the resulting solution was diluted to 1.500 L. The measured pH of the solution was 3.95.

First, we need to find the concentration of the weak acid (HA) and the concentration of the conjugate base (A-) in the initial solution. The moles of HA in the initial solution would be 0.25 mol.

Next, we need to determine the concentration of A- in the initial solution. Since the moles of A- and HA are equal at the halfway point, the concentration of A- in the initial solution would also be 0.25 M.

The pOH of the solution can be found by using the equation pOH = -log([OH-]), where [OH-] is the concentration of hydroxide ions. The pOH can be converted to pH using the equation pH = 14 - pOH.

After adding 12.00 mL of 2.90 M KOH, we can use stoichiometric calculations to find the new concentration of [OH-] and then convert it to pH using the equation pH = 14 - pOH.