2. Should the pH at the equivalence point for the titration of a weak acid and a

Question

2. Should the pH at the equivalence point for the titration of a weak acid and a strong base be neutral (pH-7), basic, or acidic? Explain your choice. Caleulate the molarity of concentrated acetie acid, HC2Hg02). The density is 1.05 3. al and it is 99.5% by mass HGHsOg. 4. Calculate the volume of concentrated HC2H,O2) needed to prepare 250 mL of 0.10 M HC HgOp). Record this volume at the top of page 23-9 of your Report Sheet. The pH of the solution is 5.83 when the moles of weak acid equals the moles of its conjugate base during a titration. What is the K, of the 5.

Explanation / Answer

2.

Since strong base produces 100 % hydroxyl ions but weak acid cannot undergo complete ionisation, hence the resulting solution at equilvalence point is in basic nature. And pH > 7.0

3.

Molarity = % * density * 10 / molar mass

M = 95.5 * 1.05 * 10 / 60

M = 16.7 M

4.

Dilution formula,

M1 * V1 = M2 * V2

16.7 * V1 = 0.10 * 250

V1 = 1.50 mL of concentrated acetic acid solution is needed.

5.

Formula for acidic buffers,

pH = pKa + Log[acid]/[conjugate base]

If [Acid] = [Conjugate base],

pH = pKa

pKa = 5.83

- LogKa = 5.83

Ka = 10-5.83

Ka = 1.45 * 10-6

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