1. Ex 5

2. Important notes Naming files
Must use the excel templates posted on the course website
Data Section of the Lab Report
Lab 5 Experiment and Calculations

3. Naming files Last name first name sect# lab #
So, if you are in Tuesday’s lab section, your name was David Ortiz and you are attempting to upload lab report 5 you should upload two files named
OrtizDavidsect2lab5.doc
and
OrtizDavidsect2lab5.xls

4. Ex 5 Preparation of 0.10 M NaOH solution
Standardization of NaOH by titration with potassium hydrogen phthalate (KHP)
Titration of a diluted commercial vinegar solution.
Propagate Uncertainty
Use data from another pair of classmates to determine if the acetic acid concentrations of red and white vinegars are significantly different.

5. Preparation of NaOH 6 mL of 50 % NaOH in 1 L
No CO2 because it precipitates as Na2CO3
Boiled water

6. Standardization of NaOH solution
Weigh g KHP and quantitatively transfer to an Erlenmeyer flask.
this about 2.5 mmol
Therefore, about 25 mL of 0.1 M NaOH will be required to titrate this weak acid
Phenolphthalein indictor (pH 8-10)
Estimate the pH at the equivalence point pH = 9
Do five samples.

7. Standardization of NaOH
Take average of the [NaOH] calculated from the each of the five trials

8. Vinegar titration

9. Concentration of HA in Vinegar
25 mL
Diluted vinegar
from pipet
Buret full of NaOH
25 mL
Vinegar
from pipet
Erylmeyer flask
250 mL
flask

10. Concentration of acetic acid (HA) in vinegar

11. Uncertainty in [HA]vinegar
s[NaOH] = ±95 % CI
sVeq(ave) = ±95 % CI
sV(dil vinegar) = ±0.03 mL
sV(flask) = ±0.12 mL
sVvinegar = ±0.03 mL

12. Uncertainty in [HA]Vinegar
Multiplication and division rule: sum of the squares
of the relative uncertainties are additive.

13. Are the [HA] in red and white vinegar statistically different?
Switch data with another set of students so that you have one set of data for red and another for white.
You need to get both the standardization data and the vinegar data from your neighbors
Perform t-test to compare the means to the 95 % CL; (N=5) for both sets
Perform F-test to see witch version of the t-test you need to use.