In your discussion you should make a conclusion and then explain how your experimental results and observations support your conclusion. The points below should help you identify the information you have available from this experiment to support your conclusion. Finish completed lab report by the due date. Be sure to include:
- a. Purpose. Based upon the introduction in the uploaded files, what are you trying to find with your experiment?
- b. Claim. Based upon the purpose of your experiment, what claim can you make using your experimental evidence?
- c. Table(s) of your results. Include expected, experimental, and % error as appropriate.
- d. Discussion of your results.
- e. Uncertainty and Error in measurements.
- Identify possible sources of uncertainty and error in your measurements.
- Use evidence from your laboratory notebook to support your error analysis.
- Discuss how the direction of each source of error affects the results.
- f. Supporting references.
Unformatted Attachment Preview
Purchase answer to see full attachment
Explanation & Answer
First, to use acid-base reactions to determine the concentration of sodium hydroxide solution.
Secondly, to determine the concentration of acetic acid in vinegar using acid-base reactions.
Finally, to help the students understand the concept of primary standard.
To carry out acid-base titrations to the required accuracy and precision in order to determine the
concentration of acetic acid in vinegar.
Sodium hydroxide absorbs water and carbon dioxide from the atmosphere, and react to form
sodium carbonate and sodium bicarbonate thus the need for standardization before acid base
Magnetic stirring plates and stir bars.
100 mL graduated cylinder.
Analytical balances (to 0.0001g).
50 mL burette.
5 mL, 10 mL, and 25 mL pipet.
Sodium hydroxide solution, unknown concentration.
Potassium hydrogen phthalate, a solid acid which has been used as a standard.
Phenolphthalein indicator solution.
Vinegar, unknown concentration.
Part 1: Standardization of sodium hydroxide solution.
1. Measure the mass of a reasonable amount of solid potassium hydrogen phthalate using
the analytical balance.
2. Dissolve the measured KHP in distilled water.
3. Add 2 to 3 drops of phenolphthalein indicator to the KHP solution.
4. Rinse the burette using sodium hydroxide solution.
5. Add sodium hydroxide solution to the burette and record the initial volume.
6. Titrate until the KHP solution just turns pink and persists even with stirring.
7. Record the final burette reading and repeat the titration three more times, recording the
Results and Discussion.
Vol NaOH Initial
Vol NaOH Final
Vol NaOH Used
The table above shows the volume of sodium hydroxide solution used to completely neutralize
potassium hydrogen phthalate solution. The volume used is obtained by subtraction the initial
volume of sodium hydroxide from the final volume as shown below.
22.5 - 0.4 = 22.1
20.4 – 0.1 = 20.3
20.8 – 0.6 = 20.2
18.2 – 0.0 = 18.2
The number of moles of potassium hydrogen phthalate can be accurately determined, for each
titration, using the mass and the molar mass of the compound.
The molar mass of KHP is 204.22 mol/g
Number of moles = Mass/ molar mass
Therefore: Where the mass is 0.8436,
No. of moles = 0.8436 g / 204.22 mol/g = 0.004131 moles
Where the mass is 0.8321,
No. of moles = 0.8321 g / 204.22 mol/g = 0.004075 moles
Where the mass is 0.8284,
No. of moles = 0.8284 g / 204.22 mol/g = 0.004056 moles
Where the mass is 0.7303,
No. of moles = 0.7303 g / 204.22 mol/g = 0.003576 moles
Sodium Hydroxide and potassium hydrogen...