titration calculations for lab flow experiment PDF

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it is calculations and answers for titration lab related to activity of buffer solution. It is experiment on labflow portal....

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Sr# 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26.

Burette readings

Volume of Acid added

Ph

1.0 1.4 1.8 2.3 2.8 3.3 3.9 4.5 5.3 5.8 6.4 7.0 7.5 8.1 8.8 9.4 10.0 10.6 11.5 12.3 13.0 13.7 19.4 20.0 20.8 21.6

0 0.4 0.8 1.3 1.8 2.3 2.9 3.5 4.3 4.8 5.4 6 6.5 7.1 7.8 8.4 9 9.6 10.5 11.3 12 12.7 18.4 19 19.8 20.6

4.10 3.89 3.92 3.54 2.98 2.86 2.76 2.51 2.52 2.50 2.46 2.35 2.34 2.32 2.24 2.22 2.18 2.15 2.12 2.09 2.05 2.04 2.03 2.02 2.00 1.98

Colour

Addition of Acid in buffer 4.5 4 3.5 3

pH

2.5 2 1.5 1 0.5 0 0

5

10

15

20

volume of acid added (mL)

Sr# 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.

Burette readings

Volume of base added

Ph

5.5 6.25 7 8.25 9.0 9.5 10.25 11 12 12.75 13.5 14.25 15 16 16.75 17.5 18.5 19.25

0 0.75 1.5 2.75 3.5 4 4.75 5.5 6.5 7.25 8 8.75 9.5 10.5 11.25 12 13 13.75

4.51 4.59 4.61 4.63 4.70 4.81 5.31 5.30 5.18 5.20 5.21 5.22 5.22 5.2 5.58 5.8 6.88 8.10

Colour

25

19. 20. 21. 22. 23. 24. 25. 26. 27.

20 21.5 22.5 23 23.8 24.5 25.2 26.0 26.7

14.5 16 17 17.5 18.3 19 19.7 20.5 21.2

8.45 9.08 10.65 11.02 11.63 11.98 12.23 12.49 12.63

Addtion of base in buffer 14 12 10

pH

8 6 4 2 0 0

5

10

15

20

25

Volume of base added (mL)

Questions Part 3: Designing and Testing Buffer Assigned buffering 0.020 M acetic acid buffer, system: target pH 5.04 Measured pH of prepared buffer solution = 4.42 =================================================================================

(14pts) Part 3: Designing and Testing Buffer You are to prepare 250.0 mL acetic acid-acetate buffer with pH of 5.04 and total concentration of 0.020 M using 0.0500 M acetic acid stock solution and 0.0500 M acetate solution. pKa of acetic acid is 4.74.

(2pts) Determine the ratio of acetate:acetic acid Note: Report your answer as a whole or decimal number. For example, a ratio of 3:2 should be reported as 1.5. [𝐶𝐻3 𝐶𝑂𝑂− ] [𝐶𝐻3 𝐶𝑂𝑂𝐻] [𝐶𝐻3 𝐶𝑂𝑂− ] [𝐶𝐻3 𝐶𝑂𝑂𝐻]

= 10𝑝𝐻−𝑝𝐾𝑎

= 105.04−4.74 = 1.995

(2pts) How many moles of acetic acid are needed? Total buffer concentration = [𝐶𝐻3 𝐶𝑂𝑂𝐻] + [𝐶𝐻3 𝐶𝑂𝑂− ] = 0.020 M [𝐶𝐻3 𝐶𝑂𝑂− ] = 1.995 [𝐶𝐻3 𝐶𝑂𝑂𝐻] Total buffer concentration = [𝐶𝐻3 𝐶𝑂𝑂𝐻] + 1.995 [𝐶𝐻3 𝐶𝑂𝑂𝐻] = 0.020 M 2.995 [𝐶𝐻3 𝐶𝑂𝑂𝐻] = 0.020 M [𝐶𝐻3 𝐶𝑂𝑂𝐻] =

0.020 M 2.995

= 0.006678 M = 0.006678 mole/L

Moles of [𝐶𝐻3 𝐶𝑂𝑂𝐻] = Molarity × volume 250

Moles of [𝐶𝐻3 𝐶𝑂𝑂𝐻] = 0.006678 mole/L ×

1000

L

Moles of [𝐶𝐻3 𝐶𝑂𝑂𝐻] = 0.0016695 mole

(2pts) How many moles of acetate are needed? [𝐶𝐻3 𝐶𝑂𝑂− ] = 1.995 [𝐶𝐻3 𝐶𝑂𝑂𝐻] = 1.995 × 0.006678 M [𝐶𝐻3 𝐶𝑂𝑂− ] = 0.01332 M = 0.01332 mole/L Moles of [𝐶𝐻3 𝐶𝑂𝑂− ] = Molarity × volume Moles of [𝐶𝐻3 𝐶𝑂𝑂− ] = 0.01332 mole/L × Moles of [𝐶𝐻3 𝐶𝑂𝑂− ] = 0.00333 moles

250 1000

L

(2pts) How many milliliters of acetic acid stock solution are needed? Molarity of Acetic acid stock solution = M = 0.0500 M = 0.0500 mol / L Moles of [𝐶𝐻3 𝐶𝑂𝑂𝐻] = 0.0016695 mole volume of Acetic acid stock solution =

0.0016695 mol 0.0500 mol / L

volume of Acetic acid stock solution = 0.03339 L = 33.39 mL

(2pts) How many milliliters of acetate stock solution are needed? Molarity of acetate stock solution = M = 0.0500 M = 0.0500 mol / L Moles of [𝐶𝐻3 𝐶𝑂𝑂− ] = 0.00333 moles volume of acetate stock solution =

0.00333 moles 0.0500 mol / L

volume of acetate stock solution = 0.0666 L = 66.6 mL

(2pts) Briefly describe how you prepared, or would prepare, the buffer solution. I took 250 mL volumetric flask. 33.39 mL from acetic acid stock solution and 66.6 mL from acetate stock solution were added to the flask. Distilled water was added in small portions with constant stirring until the volume became 250 mL.

(2pts) The actual pH measured of prepared buffer was 4.42. Determine the % error. Percentage error = Percentage error =

𝐸𝑥𝑝𝑒𝑟𝑖𝑚𝑒𝑛𝑡𝑎𝑙 𝑣𝑎𝑙𝑢𝑒 − 𝑡ℎ𝑒𝑜𝑟𝑎𝑡𝑖𝑐𝑎𝑙 𝑣𝑎𝑙𝑢𝑒 𝑇ℎ𝑒𝑜𝑟𝑎𝑡𝑖𝑐𝑎𝑙 𝑣𝑎𝑙𝑢𝑒 |4.42 − 5.04| × 5.04

100% = 12.3%

× 100%...