Directions (taken straight from lab manual):
C. pH of Buffer Solutions:
1. Preparation of Buffer Solution: Weigh 3.3 g of solid sodium acetate trihydrate, NaC2H3O2 * H2O, into a clean 150 or 250 mL beaker. Using graduated cylinders, add 46 mL of deionized water and 4.0 mL of 6.0 M HC2H3O2. Mix thoroughly. Measure 19.0 mL of this into each of two clean beakers. Label as "A" and "B". Measure the pH of this buffer solution using the remaining 10 mL.
2. Addition of Acid or Base to Buffer:
a. To the buffer in beaker "A", add 1.0 mL of 3.0 M HCl. Mix thoroughly and read the pH of the resulting mixture.
b. To the buffer in beaker "B,", add 1.0 mL of 3.0 M NAOH. Mix thoroughly and read the pH of the resulting mixture.
3. pH of Deionized water: Obtain 19 mL of deionized water in each of two beakers. Read the pH of the deionized water. (NOTE: It will not be a pH of 7.00.)
4. Addition of Acid or Base to Deionized Water:
a. To one beaker of deionized water, add 1.0 mL of 3.0 M HCl. Mix thoroughly and read the pH of the resulting mixture.
b. To the second beaker of deionized water, add 1.0 mL of 3.0 M NAOH. Mix thoroughly and read the pH of the resulting mixture.
[H+] Buffer 1.74 x 10-5 M Buffer + HCl 3.44 x 10-5 M Buffer + NaOH 8.83 x 10-6 M Water 1.0 x 10-7 M Water + HCl Water + NaOH
Measured pH Calculated pH
(from [H+] above)
Buffer 4.96 Buffer + HCl 4.57 Buffer + NaOH 5.08 Water 5.40 Water + HCl 1.71 Water + NaOH 12.14
Task:
1. Calculate the pH for each.
2. Compare and explain the difference in pH change occurring for the buffer system and for the water on the addition of HCl.
Directions (taken straight from lab manual):
C. pH of Buffer Solutions:
1. Preparation of Buffer Solution: Weigh 3.3 g of solid sodium acetate trihydrate, NaC2H3O2 * H2O, into a clean 150 or 250 mL beaker. Using graduated cylinders, add 46 mL of deionized water and 4.0 mL of 6.0 M HC2H3O2. Mix thoroughly. Measure 19.0 mL of this into each of two clean beakers. Label as "A" and "B". Measure the pH of this buffer solution using the remaining 10 mL.
2. Addition of Acid or Base to Buffer:
a. To the buffer in beaker "A", add 1.0 mL of 3.0 M HCl. Mix thoroughly and read the pH of the resulting mixture.
b. To the buffer in beaker "B,", add 1.0 mL of 3.0 M NAOH. Mix thoroughly and read the pH of the resulting mixture.
3. pH of Deionized water: Obtain 19 mL of deionized water in each of two beakers. Read the pH of the deionized water. (NOTE: It will not be a pH of 7.00.)
4. Addition of Acid or Base to Deionized Water:
a. To one beaker of deionized water, add 1.0 mL of 3.0 M HCl. Mix thoroughly and read the pH of the resulting mixture.
b. To the second beaker of deionized water, add 1.0 mL of 3.0 M NAOH. Mix thoroughly and read the pH of the resulting mixture.
| [H+] | |
| Buffer | 1.74 x 10-5 M |
| Buffer + HCl | 3.44 x 10-5 M |
| Buffer + NaOH | 8.83 x 10-6 M |
| Water | 1.0 x 10-7 M |
| Water + HCl | |
| Water + NaOH |
| Measured pH | Calculated pH (from [H+] above) | |
| Buffer | 4.96 | |
| Buffer + HCl | 4.57 | |
| Buffer + NaOH | 5.08 | |
| Water | 5.40 | |
| Water + HCl | 1.71 | |
| Water + NaOH | 12.14 |
Task:
1. Calculate the pH for each.
2. Compare and explain the difference in pH change occurring for the buffer system and for the water on the addition of HCl.
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