Question

er solutions can be produced by mixing a weak acid with its conjugate base or by mixing a weak base with its conjugate acid. The Henderson-Hasselbalch equation, pH=pKa+log[base][acid] allows you to calculate the pH of a buffer. Note that molarity, moles, and millimoles are all proportional, so you can substitute the number moles, or millimoles, for the concentration terms in this formula. Part A You need to produce a buffer solution that has a pH of 5.03. You already have a solution that contains 10. mmol (millimoles) of acetic acid. How many millimoles of acetate (the conjugate base of acetic acid) will you need to add to this solution? The pKa of acetic acid is 4.74.

Answer 1

Answer:

You need to add 19,5 mmol of acetates

Explanation:

Using the Henderson-Hasselbalch equation:

pH = pKa + log₁₀ [base]/[acid]

For the buffer of acetates:

pH = pKa + log₁₀ [CH₃COO⁻]/[CH₃COOH]

As pH you want is 5,03, pka is 4,74 and milimoles of acetic acid are 10:

5,03 = 4,74 + log₁₀ [CH₃COO⁻]/[10]

1,95 = [CH₃COO⁻]/[10]

[CH₃COO⁻] = 19,5 milimoles

Thus, to produce an acetate buffer of 5,03 having 10 mmol of acetic acid, you need to add 19,5 mmol of acetates.

I hope it helps!