K_{a} of acetic acid

background [prelab (15 points) due at the beginning of lab]

describe how to determine K

_{a}using data from the titration curve based on thepH of the acetic acid solution prior to titration using the definition of K

_{a}pH at 1/2 equilivalence point using the Henderson - Hasselbalch equation

sketch a data table for this lab containing entries for all required experimental measurements (i.e. review purpose & content of lab report)

purpose

assess the accuracy of the determination of K

_{a}of acetic acid using the above methodsidentify the "buffer region" in the titration curve

compare the pH at the equivalence point: calculated value versus experimental value

materials

vinegar (i.e. acetic acid; ~30 mL); NaOH (~ 0.5 M)

beaker; buret; ring stand with buret clamp; pH meter

methods / data analysis [delegate lab work]

student design, includes

student preparationof a known [NaOH] solutionrefer to prior lab in the calibration of the pH probe [before lab !]

Content of the lab report [35 points]

data analysis (25 points)

titration curve & a plot of its first derivative

determination of the K

_{a}of acetic acid using the above 2 methods - based on your group's data (show your work)calculate the pH at equivalence point based on the concentration & volume of the acetic acid solution

statistical analysis (include interpretation of p-value; use appropriate statistical test(s); see purpose; there's more than one method to analyze the data)

discussion (10 points)

based on the statistical analysis, discuss the accuracy in each method to determine the K

_{a}of acetic acidreferring to the titration curve, define the term "buffer capacity" & "buffer region"

**resources**:

lab activity source (examples): site 1 & site 2 [access 4 / 2009]