Question

What volume of 0.100 M NaOH is needed to make 100.0 mL of a buffer solution with a pH of 6.00 if one starts with 50.0 mL of 0.100 M potassium hydrogen phthalate? The K a2 for potassium hydrogen phthalate is 3.1 × 10-6. 30.2 mL 37.8 mL 22.4 mL 27.6 mL

Answer 1

To make a buffer solution with a pH of 6.00, 224 mL of 0.100 M NaOH is needed.

Step-by-step explanation:

To determine the volume of 0.100 M NaOH needed to make 100.0 mL of a buffer solution with a pH of 6.00, we can use the Henderson-Hasselbalch equation:

pH = pKa + log([A-]/[HA])

Using the given information and rearranging the equation, we can solve for [A-] (the concentration of the conjugate base):

[A-] = 10^(pH - pKa) * [HA]

Substituting the values we have:

[A-] = 10^(6.00 - 4.74) * 0.100 M = 22.4 * 0.100 M = 2.24 M

Since the concentration of NaOH is 0.100 M, we can calculate the volume using the formula:

Volume = ([A-] * Vfinal) / [NaOH]

Volume = (2.24 M * 100 mL) / 0.100 M = 2.24 * 100 mL = 224 mL

Therefore, the volume of 0.100 M NaOH needed is 224 mL.