Map What concentrations of acetic acid (pKa = 4.76) and acetate would be require

Question

Map What concentrations of acetic acid (pKa = 4.76) and acetate would be required to prepare a 0.15 M buffer solution at pH 4.5? Note that the concentration and/or pH value may differ from that in the first question STRATEGY 1. Rearrange the Henderson-Hasselbalch equation to solve for the ratio of base (acetate) to acid (acetic acid), [A YHA 2. Use the mole fraction of acetate to calculate the concentration of acetate. 3. Calculate the concentration of acetic acid. Step 1: Rearrange the Henderson Hasselbalch equation to solve for HA The Henderson-Hasselbalch equation is A-1 HA equation to solve for H the solution is at pHt 4 5. efor HA Use the Henderson-Hasselbalch equation to solve forA Enter your answer as a number. For example, 9.6. Do not enter a formula like 106*2 Number Exi- Exit- Check Answer 0 Nek Check Answer O Ne View Saltalicen ( Previous ..e Up & View Sci tion 0 Previous Gitte Up Hint

Explanation / Answer

Henderson-Hasselbalch equation:

pH = pKa + log([A-]/[HA])
Clear ([A-]/[HA]):
([A-]/[HA]) = 10pH - pKa
([A-]/[HA]) = 104.5 - 4.76
([A-]/[HA]) = 0.545

[HA] + [A-] = buffer concentration
([A-]/[HA]) = 0.545
[HA] = [A-]/0.545
[A-]/0.545 + [A-] = 0.15 M

Clear [A-]:
[A-] ((1/0.545) + 1) = 0.15 M
[A-] ((1.835) + 1) = 0.15 M
[A-] (2.835) = 0.15 M
[A-] = 0.15 M/2.835
[A-] = 0.053 M
*concentration of acetate

Calculate concentration of acetic acid:
[HA] + [A-] = 0.15 M
[HA] = 0.15 M - [A-]
[HA] = 0.15 M - 0.053 M
[HA] = 0.097 M
*concentration of acetic acid

______________________________

Calculate pH of the solution:
[A-] = 0.053 M
[HA] = 0.097 M

pH = 4.76 + log(0.053 M/0.097 M)
pH = 4.5

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