Data Sheets (To be attached to your lab report. Recopy if messy): Unknown Letter
ID: 926307 • Letter: D
Question
Data Sheets (To be attached to your lab report. Recopy if messy):
Unknown Letter: Triprotic Molarity of NaOH (mol/L) _____________
Volume of unknown acid (mL):
Run 1
Run 2
Run 3
Initial volume NaOH
0.00
8.80
17.45
Final Volume NaOH
8.80
17.45
26.20
NaOH volume added (subtract B - A)
8.80
8.65
8.75
Moles NaOH added
Analysis:
Molarity of unknown acid (assuming the acid is triprotic):
Run 2 _____________ Run 3 _____________ Average _____________
Sample Calculation of Molarity of unknown acid:
Post Lab Questions:
1. Why is it important to record the endpoint of the titration at the permanent faint pink color as opposed to the permanent dark pink color?
2. What would happen to your calculated acid concentration if your final solution was too pink?
3. Calculate the molarity of the unknown acid if the acid were:
triprotic
4. Why is the stir bar used?
5. Would it be possible to do this experiment without using an indicator dye? If so, explain how.
6. Is the titration technique limited to acid/base reactions?
Run 1
Run 2
Run 3
Initial volume NaOH
0.00
8.80
17.45
Final Volume NaOH
8.80
17.45
26.20
NaOH volume added (subtract B - A)
8.80
8.65
8.75
Moles NaOH added
Explanation / Answer
Post Lab Questions:
1. Why is it important to record the endpoint of the titration at the permanent faint pink color as opposed to the permanent dark pink color?
Ans: The indicator is very sensitive and depends on the pH. The moment it reaches the equivalence point, it becomes faint pink, the actual amount to be recorded.
2. What would happen to your calculated acid concentration if your final solution was too pink?
Ans: The solution was too pink means the solution became alkaline rather than neutral and this could happen if the addition of base was slightly more which will give wrong calculation.
3. Calculate the molarity of the unknown acid if the acid were: triprotic
Ans: in sufficient data.
4. Why is the stir bar used?
Ans: Stir bar makes the solution homogeneous otherwise local titration would happen and faulty result will be the outcome.
5. Would it be possible to do this experiment without using an indicator dye? If so, explain how.
Ans: If the acid has any color and acts an indicator then, external indicator will not be required.
6. Is the titration technique limited to acid/base reactions?
Ans: Titration is measuring the concentration of one unknown against a known concentration, it could for any solution which change forms with other reagents of known concentration.
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