Consider the titration of a 50.0 mL sample of a 0.100 M solution of the triprotic weak acid citric acid (H3C6H5O7) with 0.100 M KOH. For citric acid, the three (3) acid dissociation constant values are ka1 = 7.40x10-3, ka2 = 1.70x10-5, and ka3 = 4.00x10-7, respectively. Given this information, calculate the pH upon addition of each of the following volume of KOH to the citric acid solution during this titration:

a) 25 mL KOH added
b) 50 mL KOH added
c) 75 mL KOH added
d) 100 mL KOH added
e) 125 mL KOH added

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To calculate the pH upon adding each volume of KOH, we need to determine the moles of citric acid and KOH present, and then calculate the concentration of the resulting solution. Using the acid dissociation constants, we can then calculate the pH.

Let's go through the steps for each case:

a) 25 mL KOH added

Step 1: Moles of citric acid and KOH
- The initial volume of citric acid is 50.0 mL, which is equal to 0.0500 L.
- Given that the concentration of citric acid is 0.100 M, we can calculate the moles of citric acid: Moles of citric acid = concentration × volume = 0.100 M × 0.0500 L = 0.00500 moles.
- The volume of KOH added is 25 mL, which is equal to 0.0250 L.
- Given that the concentration of KOH is 0.100 M, we can calculate the moles of KOH: Moles of KOH = concentration × volume = 0.100 M × 0.0250 L = 0.00250 moles.

Step 2: Reaction between citric acid (H3C6H5O7) and KOH
The balanced chemical equation for the reaction between citric acid and KOH is:
H3C6H5O7 (aq) + 3 KOH (aq) → 3 KC6H5O7 (aq) + 3 H2O (l)

Since the ratio between citric acid and KOH is 1:3, all the moles of KOH will be consumed, but there will still be some moles of citric acid left.

Moles of citric acid remaining = Initial moles of citric acid - Moles of KOH consumed = 0.00500 moles - 0.00250 moles = 0.00250 moles.

Step 3: Calculate the concentration of citric acid in the remaining solution
The volume of the resulting solution is the sum of the initial volume of citric acid and the volume of KOH added:
Volume of resulting solution = Initial volume of citric acid + Volume of KOH added = 0.0500 L + 0.0250 L = 0.0750 L.

The concentration of the remaining citric acid is then:
Concentration of citric acid = Moles of citric acid remaining / Volume of resulting solution = 0.00250 moles / 0.0750 L = 0.0333 M.

Step 4: Calculating the pH
To calculate the pH, we need to find the concentration of H+ ions in solution. The pH can be determined using the acid dissociation constant (Ka) for citric acid. In this case, we need to consider Ka1.

Ka1 = [H+][C6H5O7-] / [H3C6H5O7]

[H+] represents the concentration of H+ ions, [C6H5O7-] represents the concentration of the conjugate base of citric acid (KC6H5O7), and [H3C6H5O7] represents the concentration of citric acid.

[H+] = [H3C6H5O7] × Ka1 / [C6H5O7-] = 0.0333 M × 7.40x10-3 / 0.0333 M = 7.40x10-3 M.

To find the pH, we use the equation: pH = -log[H+].
pH = -log(7.40x10-3) = 2.13.

Therefore, upon adding 25 mL of KOH to the citric acid solution, the pH will be 2.13.

We can follow the same steps for the remaining cases: b) 50 mL KOH added, c) 75 mL KOH added, d) 100 mL KOH added, and e) 125 mL KOH added. The only difference is that the volume of KOH added and the remaining moles of citric acid will change, leading to different concentrations of citric acid and different pH values upon each addition.