Purpose:
1.
To determine the reaction between an acid and a base.
2.
To standardize a base then use this base to determine the concentration of acetic acid in household vinegar.
Materials:
0.150 M HCl
Unknown concentration of
NaOH
2 x 150 mL beakers
2 x 150 mL Erlenmeyer flasks
2 x 50.00 mL burets
Lab stand
Buret clamp
Phenolphthalein
Safety:
1.
Hydrochloric Acid and sodium hydroxide are corrosive. Wash up spills with plenty of water.
2.
Safety glasses are required at all times.
Procedure:
PART ONE Standardization of Sodium Hydroxide
1.
Obtain two burets. Rinse one with about 10 mL of HCl three times making sure to allow sufficient HCl to run to the tip each time. Rinse the other with NaOH in the same way.
2.
Fill the one buret to the top with the HCl and clear the air space in the tip. Repeat this with the NaOH buret.
3.
Record the initial volume of both burets in the appropriate spot in the data section.
4.
Allow about 15 mL of HCl to run into the 125 mL Erlenmeyer flask.
5.
Add three drops of phenolphthalein to the HCl and about 10 - 15 mL of distilled water.
6.
Titrate the NaOH solution into the Erlenmeyer flask until you get a persistent faint pink color. If you go beyond the endpoint (too dark pink) add a few drops of HCl and then continue adding NaOH until you reach the endpoint.
7.
Record the final volume of the HCl and NaOH in the appropriate spot in the data section.
8.
Refill the burets and repeat the titration (steps 2 - 7) two more times.
PART TWO Determination of Acid Concentration
1.
Empty out the HCl buret and rinse it three times with water then fill it with distilled water and put it away.
2.
Refill the NaOH buret. You will get the vinegar from the buret at the front of the lab.
3.
Record the initial volume of both burets in your data section.
4.
Allow between 5 and 7 mL of vinegar to run into the 125 mL Erlenmeyer flask.
5.
Add three drops of phenolphthalein to the vinegar and about 10 - 15 mL of distilled water.
6.
Titrate the NaOH solution into the Erlenmeyer flask until you get a persistent faint pink color. If you go beyond the endpoint (too dark pink) add a few drops of vinegar then continue adding NaOH until you just reach the endpoint.
7.
Record the final volume of vinegar and NaOH in your data section.
8.
Refill the burets and repeat the titration (steps 2 - 7) two more times.

Data
PART ONE Standardization of Base
Trial 1
Initial Volume of HCl....................................................................... ________ mL
Final Volume of HCl......................................................................... ________ mL
Volume of HCl Used......................................................................... ________ mL
Concentration of HCl....................................................................... ________ M
Moles of HCl determined............................................................... ________ mol
Initial Volume of NaOH ................................................................. ________ mL
Final Volume of NaOH.................................................................... ________ mL
Volume of NaOH used..................................................................... ________ mL
Moles of NaOH determined......................................................... ________ mol
Concentration NaOH determined............................................. _________ M
Average Concentration NaOH.................................................... _________M
PART TWO Determination of Acid Concentration
Trial 1
Initial Volume of NaOH.................................................................. ________ mL
Final Volume of NaOH.................................................................... ________ mL
Volume of NaOH Used.................................................................... ________ mL
Concentration of NaOH.................................................................. ________ M
Moles of NaOH determined.......................................................... ________ mol
Trial 2
_______ mL
________ mL
________ mL
________M
________ mol
________ mL
________ mL
________ mL
________ mol
________ M
Trial 2
Trial 3
________mL
________ mL
________ mL
________M
________ mol
________ mL
________ mL
________ mL
________ mol
________ M
Trial 3
Initial Volume of Vinegar ............................................................. ________ mL
Final Volume of Vinegar................................................................ ________ mL
Volume of NaOH Vinegar.............................................................. ________ mL
Moles of Vinegar determined...................................................... ________ mol
Concentration Vinegar determined.......................................... ________ M
Average Concentration Vinegar................................................. ___________M
Questions:
_______ mL
________ mL
________ mL
________M
________ mol
________ mL
________ mL
________ mL
________ mol
________ M
________mL
________ mL
________ mL
________M
________ mol
________ mL
________ mL
________ mL
________ mol
________ M
1.
From your knowledge of reactions write and balance the reaction between HCl and NaOH.
2.
From the concentration given and the volume used, calculate the number of moles of HCl involved in each titration in Part 1. Record this value in the data section.
3.
Use the equation for the reaction to calculate the number of moles of NaOH, the base, that are used per mole of HCl, the acid, in Part 1.
4.
From the relationship in question 3, determine the number of moles of base actually used for each trial.
Record these in the data section.
5.
Calculate the molar concentration of the NaOH for each trial. Record this in the data section, including the average [NaOH].
6.
From your knowledge of reactions write and balance the reaction between vinegar (acetic acid) and
NaOH.
7.
From the concentration given and the volume used, calculate the number of moles of NaOH involved in each titration in part 2. Record this value in the data section.
8.
Use the equation for the reaction to calculate the number of moles of acetic acid that are used per mole of
NaOH in part 2.
9.
From the relationship in question 8, determine the number of moles ace acetic acid actually used for each trial. Record these in the data section.
10.
Calculate the molar concentration of the acetic acid for each trial. Record this in the data section, including the average [acetic acid].
11.
Calculate the percent acetic acid in vinegar by weight.
Conclusion: