K_a of acetic acid

background [prelab (10 points) due at the beginning of lab]

describe how to determine K_a using data from the titration curve based on the

pH 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 methods

identify 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 (~75 mL, 0.4 M)

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

methods / data analysis [delegate lab work]

student design, includes student preparation of a known [NaOH] solution

refer 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; there should be 3 statistical tests done)

discussion (10 points)

based on the statistical analysis, discuss the accuracy in each method to determine the K_a of acetic acid

referring to the titration curve, define the term "buffer capacity" & "buffer region"

resources:

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