Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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Question
Data in first picture and questjons in second
![9. Calculate the initial concentration of your acid. Recall that the original volume of the solution was
0.100 L
[Acid] initial
Using your calculated value of K, and the initial concentration of the acid, calculate the initial pH of
your acid,
Set up the ICE table. You may need to use the quadratic formula.
Initial pH from the titration:
Calculated initial pH:
Was the calculated initial pH higher or lower than initial pH from the curve ? Calculate the % error.
10. Look up the actual literature value of the pKa of your unknown in an appropriate source. (CRC
handbook or the NIST webbook)
Literature value of pka =
(List both pka's if your acid is polyprotic)
Source of the data :
Was the actual value higher or lower than the pKa from your graph? Calculate the % error.
Calculated pKa
1](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F4e538c25-204f-4711-955d-bf3549a46172%2F1e7c80ff-b95a-4b13-83c5-9c7b3c7577f9%2Fw4tmalo_processed.jpeg&w=3840&q=75)
Transcribed Image Text:9. Calculate the initial concentration of your acid. Recall that the original volume of the solution was
0.100 L
[Acid] initial
Using your calculated value of K, and the initial concentration of the acid, calculate the initial pH of
your acid,
Set up the ICE table. You may need to use the quadratic formula.
Initial pH from the titration:
Calculated initial pH:
Was the calculated initial pH higher or lower than initial pH from the curve ? Calculate the % error.
10. Look up the actual literature value of the pKa of your unknown in an appropriate source. (CRC
handbook or the NIST webbook)
Literature value of pka =
(List both pka's if your acid is polyprotic)
Source of the data :
Was the actual value higher or lower than the pKa from your graph? Calculate the % error.
Calculated pKa
1
Transcribed Image Text:Data Sheet:
Unknown acid #9
Mass of the Unknown acid: 2
0.209
PH
364 3.26
369 3:24
3:26
3.28
3.21
3:30
3:35
Name:
Volume NaOH added
0.5ml
Unknown acid
(letter or number on the unknown bottle)
#9 Concentration of NaOH(aq):
1.
Aml
15mi
2.0ml
2.5ml
30ml
3.5mi
toml
4.5ml
20ml
5.Smi
6.0m)
6.5ml
10ml
75ml
80ml
8.5ml 1
9.0ml
9.5ml
100ml
10 sml
11.0m
11.5ml
12.0ml
12.5 ml
13.0 ml
B S ml
14.0 ml
14.5 ml
15.0 ml
#9
23.51
3.54
3.58
3.64
3.72
3.39
3.70
3867
3.93
$4.00
14.06
4:13
47 4.20
4.28 FAT
4.36
4.43
4.46
4.64
4.83
5.05
2.93
9.91
Partner's Names:
Titration of a weak Acid: Calculations and Post lab questions
Volume NaOH added
15.5ml
16.0 ml
16.5 ml
(70ml
175ml
(letter or number on unknown bottle)
0.0995 M
pH
10.63
10:03
11.25
11.37
Mass of Unknown acid:
0.0995
Concentration of NaOH(aq):
Plot the titration curve as pH vs. mL of NaOH added using a computer graphing program. Make sure
you have chosen the correct X and Y axes. Please include gridlines and print out a 8 ½ x 11 plot. You
must attach the graph to the Lab Report.
02059
2. Locate the equivalence point(s) on the titration curve. It is very unlikely that the equivalence point(s)
will be actual data points. You will need to either manually draw a smooth curve connecting your data
points, or select the option in your graphing program that will draw the best-fit curve for you. Then find
the steepest point(s) on the curve. This is/these are the equivalence point(s). Label the equivalence
point(s) on the curve. (For polyprotic acids, label all the equivaence points.)
3. How many equivalence points does your graph show?
1
4. Recall that at the first equivalence point, moles of acid = moles of base added.
Volume of NaOH added at the first equivalence point:
14.9ML
1.48x10 mol
Moles of NaOH added at the first equivalence point:
Volume of NaOH added at the Second equivalence point (if your unknown is polyprotic) only 1 equivalerile
poin
VON me of NaOH aF Ist equivalence = 14.9ml
5. Use the mass of the acid, the concentration of NaOH and the volume of NaOH added at the first
equivalence point to calculate the molar mass of the acid: (Show your work clearly and include proper
mass of Unknown -0.2099 Concentration of NaOH = 00995 M
units.)
mass of and
= 0.2099
molar mass of and
=
1.48x10m ² 141.21 g/mol
Calculated Molar mass of the unknown acid=141.21 g/mol
6. Label the areas of the curve where a buffer is present. Locate the point where pH=pKa (halfway to
the equivalence point.) Label pKa on the graph. If the acid is polyprotic, label the pKa for each
equivalence point on the graph.
Done!!! pka=4
5
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