Question

I performed an experiment to find the equivalent mass anddissociation constant of an unknown weak acid by titrimetry.

My data is the following:

A.) Determining a satisfactory sample size for the unknown weakacid:

Mass of unknown acid, 0.12 grams

Final buret reading: 5.6 mL

Initial buret reading: 0.0mL

Volume of NaOH solution required: 5.6mL

Mass of unknown acid requiring 25mL of NaOH solution fortitration: 0.54grams

Volume of NaOH solution required: 300mL

Molarity of NaOH solution: 0.25M

B.) Titrating a sample of an unknown weak acid

Mass of weighing paper plus unknown acid: 0.91grams

Mass of weighing paper: 0.37 grams

Mass of unknown acid: 0.54grams

C.) Buret readings of first and second determinations:

First determination:

13.5mL = 3.82 pH

26.5mL = 7.60 pH

Second determination:

13.5mL = 3.74 pH

27.0mL = 7.60 pH

pKa of acid: 3.82 / 3.74

Ka: 1.85x10^-4 / 1.82x10^-4

Find the following for both determinations 1 and 2:

Volume of NaOH solution required to reach equivalence point, mL:?

Number of equivalents of NaOH required to reach equivalencepoint: ?

Number of equivalents of unknown acid titrated, equiv: ?

Equivalent mass of unknown acid, g/equiv: ?