Part II. Determination Ka and Molar Mass of Unknown Monoprotic Acio

Chemistry: Principles and Practice
3rd Edition
ISBN:9780534420123
Author:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward Mercer
Publisher:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward Mercer
Chapter16: Reactions Between Acids And Bases
Section: Chapter Questions
Problem 16.54QE
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Please check if my second data table is correct. I don't think the molar mass is correct

Part II. Determination Ka and Molar Mass of Unknown Monoprotic Acid
Assignment # 2
1
Mass of the acid, in stock solution, g
4.45
2
Volume of the stock solution, ml
250.00
3
Molarity of the standardized NaOH solution, M
0.09
Data Table 1. Titration Data
1
Volume of the Unknown acid used for titration, mL
10.00
Volume of NaOH at equivalence point from first derivative, ml
3 Volume of NaOH at equivalence point from second derivative, mL
2
22.13
22.13
4
Average volume of NaOH for calculations
22.13
Initial pH
3.08
6
pH at equivalence point from Titration Curve Page
8.76
6
pH at half-equivalence point from Titration Curve Page
4.93
7
pH at half-equivalence point from the Graph below
9.15
Data Table 2. Final Results of the Titration of Unknown Acid
Moles of NaOH at equivalence point, mol|
Moles of Unknown acid at equivalence point, mol
Molarity of Unknown acid, M
Moles of Unknown acid in the stock solution, mol
Molar Mass of Unknown acid, g/mol
pH at half-equivalence point
2.02E-03
2.02E-03
8.09E-03
2.02E-03
74.08
3
4
4.93
7
pKa
4.93
8
Ка
1.17E-05
According to Appendix II Unknown acid is identified as
Propanoic Acid
2.
Transcribed Image Text:Part II. Determination Ka and Molar Mass of Unknown Monoprotic Acid Assignment # 2 1 Mass of the acid, in stock solution, g 4.45 2 Volume of the stock solution, ml 250.00 3 Molarity of the standardized NaOH solution, M 0.09 Data Table 1. Titration Data 1 Volume of the Unknown acid used for titration, mL 10.00 Volume of NaOH at equivalence point from first derivative, ml 3 Volume of NaOH at equivalence point from second derivative, mL 2 22.13 22.13 4 Average volume of NaOH for calculations 22.13 Initial pH 3.08 6 pH at equivalence point from Titration Curve Page 8.76 6 pH at half-equivalence point from Titration Curve Page 4.93 7 pH at half-equivalence point from the Graph below 9.15 Data Table 2. Final Results of the Titration of Unknown Acid Moles of NaOH at equivalence point, mol| Moles of Unknown acid at equivalence point, mol Molarity of Unknown acid, M Moles of Unknown acid in the stock solution, mol Molar Mass of Unknown acid, g/mol pH at half-equivalence point 2.02E-03 2.02E-03 8.09E-03 2.02E-03 74.08 3 4 4.93 7 pKa 4.93 8 Ка 1.17E-05 According to Appendix II Unknown acid is identified as Propanoic Acid 2.
Titration Curve - pH vs Volume
13.00
12.00
11.00
10.00
9.00
8.00
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
Volume of NaOH, ml
Equation 1 (Eq 1)
y= 0.08x+4.0474
Slope (ml)
0.0800
Intercept (b1)
4.0474
Equation 2 (Eq 2)
y= 4.804x-97.314
Slope (m2)
4.804
Intercept (b2)
-97.31
Equation 3 (Eq 3)
y=0.062x-10.348
Slope (m2)
0.0620
Intercept (b3)
10.348
V1, Volume of NAOH, ml at intercept of Eq 1 and Eq 2
21.46
(b2 - b1) (m1 - m2)
v2, Volume of NAOH, ml at intercept of Eq 2 and Eq 3
22.70
(b3 - b1) (m2 - m3)
Veg, Volume of NAOH, mL at equivalence point
(V2 • V1) /2
22.08
pHeq, pH at equivalence point
8.76
m2 x Veq • b2
Vhalf-eq, Volume of NaOH, ml at half - equivalence point
11.04
Veq 12
pH half-eq, pH at half - equivalence point
4.93
m1x Vhalf-eq • b1
pKa
4.93
Ка
1.17E-05
Hd
Transcribed Image Text:Titration Curve - pH vs Volume 13.00 12.00 11.00 10.00 9.00 8.00 7.00 6.00 5.00 4.00 3.00 2.00 1.00 0.00 0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 Volume of NaOH, ml Equation 1 (Eq 1) y= 0.08x+4.0474 Slope (ml) 0.0800 Intercept (b1) 4.0474 Equation 2 (Eq 2) y= 4.804x-97.314 Slope (m2) 4.804 Intercept (b2) -97.31 Equation 3 (Eq 3) y=0.062x-10.348 Slope (m2) 0.0620 Intercept (b3) 10.348 V1, Volume of NAOH, ml at intercept of Eq 1 and Eq 2 21.46 (b2 - b1) (m1 - m2) v2, Volume of NAOH, ml at intercept of Eq 2 and Eq 3 22.70 (b3 - b1) (m2 - m3) Veg, Volume of NAOH, mL at equivalence point (V2 • V1) /2 22.08 pHeq, pH at equivalence point 8.76 m2 x Veq • b2 Vhalf-eq, Volume of NaOH, ml at half - equivalence point 11.04 Veq 12 pH half-eq, pH at half - equivalence point 4.93 m1x Vhalf-eq • b1 pKa 4.93 Ка 1.17E-05 Hd
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