Question about Titration

Second method for determining the Ka of acetic acid by titration with NaOH.

I would like to see the details of the calculations. For my lab experiment I have the following data:

Titration#1

4 drops of methyl red indicator (to show endpoint).
Burette fill with 50ml of 0.1 M NaOH.
Titrate by adding 1ml increments of NaOH.
Continue titration past the endpoint to a pH of 11-12.

QUESTIONS:

1. Determine the pH at the point in which the acetate ion concetration equals the acetic acid concentration. (that is where the acetic acid is 50% ionized). Record this pH value. (ANSWER IS pH = 5.0)

2. The pKa of an acid equals the pH of the solution when 50% of the acid has been ionized. What is the pKa of acetic acid? Calculate the Ka as well. Example: pH = pKa + log[A-]/[HA]

3. Look up the pKa and Ka for acetic acid and record them here.(compare your results from #2 above to the standard or accepted pKa and Ka)

4. Look up the accepted value for the Ka acetic acid in a handbook or on the internet. Calculate the percent error between the experimental and accepted values according to:
% error = / experimental Ka - accepted Ka /
accepted Ka * 100%