2.1 Calculate the pH of 1.0 M HC2H3O2 solution, using Ka = 1.7 × 10-5 . Begin this calculation by defining the variable x. List the pH answer as “theoretical pH” on the report sheet. Have the instructor check this answer and all subsequent calculations. To test your prediction, obtain about 35 mL 1.0 M HC2H3O2 and add to a clean, dry 50 mL beaker. Measure the pH of this solution. Be sure the electrode is properly submerged and gives a stable reading. Record the pH reading in the “Observed pH” column on the report sheet. The value should be within ± 0.2 pH units of the calculated value. From the experimental pH and beginning concentrations of the solution components, calculate the remainder of the entries across the table to pKa . Save this solution for Sections 2.3 and 2.6. 2.2 Calculate the pH of 0.10 M HC2H3O2 solution. List this answer as “theoretical pH” on the report sheet. Test your prediction by placing 5 mL of 0.10 M HC2H3O2 in a test tube and testing its pH. Record this pH on your report sheet. Place this solution in your waste holding beaker. 2.3 Calculate the pH of a solution made by mixing 20.0 mL of 1.0 M NaC2H3O2 solution with 8.0 mL 1.0 M HC2H3O2 solution. Note that in this calculation [H3O+ ] ≠ [C2H2O2- ] . List this as “theoretical pH” on your report sheet. Measure about 8.0 mL of the 1.0 M HC2H3O2 solution from 2.1 in a small graduated cylinder. Discard the rest of the solution into your waste holding beaker, then dry out the beaker. Pour the 8.0 mL portion from the cylinder back into the dried beaker. Add 20.0 mL 1.0 M NaC2H3O2 solution. Measure the pH of this solution and record. Save this solution for section 2.4. ‘/ 2.4 Calculate the pH of a new solution made by taking 10.0 mL of the solution in 2.3 and diluting it to 45.0 mL with deionized water. Enter this as “theoretical pH” on the report sheet. Measure out 10.0 mL of the solution in 2.3 with a small graduated cylinder and pour this into a larger graduated cylinder. Add, from your wash bottle, deionized water to the 45 mL level. Mix this solution well and pour this mixture into a clean, dry 50 or 100 mL beaker. Measure the pH of this diluted solution. 2.5 Calculate the pH of a solution made by mixing 3.0 mL of 1.0 M NaC2H3O2 with 18.0 mL of 1.0 M HC2H3O2 . List this as “theoretical pH” on the report sheet. Measure 18.0 mL of 1.0 M HC2H3O2 that you saved in 2.1 and pour into a clean, dry 50 mL beaker. Then add 3.0 mL of 1.0 M NaC2H3O2 solution and measure the pH. Record this value. 2.6 Place 20.0 mL of 1.0 M HC2H3O2 in your 50 mL beaker. Add 4 drops of methyl orange indicator. Measure the pH and note the color of the solution. Now add about a spoonful of solid NaC2H3O2 and stir to dissolve. Measure the pH again and note the color of this solution.
2.1 Calculate the pH of 1.0 M HC2H3O2 solution, using Ka = 1.7 × 10-5 . Begin this calculation by defining the variable x. List the pH answer as “theoretical pH” on the report sheet. Have the instructor check this answer and all subsequent calculations.
To test your prediction, obtain about 35 mL 1.0 M HC2H3O2 and add to a clean, dry 50 mL beaker. Measure the pH of this solution. Be sure the electrode is properly submerged and gives a stable reading. Record the pH reading in the “Observed pH” column on the report sheet. The value should be within ± 0.2 pH units of the calculated value. From the experimental pH and beginning concentrations of the solution components, calculate the remainder of the entries across the table to pKa . Save this solution for Sections 2.3 and 2.6.
2.2 Calculate the pH of 0.10 M HC2H3O2 solution. List this answer as “theoretical pH” on the report sheet.
Test your prediction by placing 5 mL of 0.10 M HC2H3O2 in a test tube and testing its pH. Record this pH on your report sheet. Place this solution in your waste holding beaker.
2.3 Calculate the pH of a solution made by mixing 20.0 mL of 1.0 M NaC2H3O2 solution with 8.0 mL 1.0 M HC2H3O2 solution. Note that in this calculation [H3O+ ] ≠ [C2H2O2- ] . List this as “theoretical pH” on your report sheet.
Measure about 8.0 mL of the 1.0 M HC2H3O2 solution from 2.1 in a small graduated cylinder. Discard the rest of the solution into your waste holding beaker, then dry out the beaker. Pour the 8.0 mL portion from the cylinder back into the dried beaker. Add 20.0 mL 1.0 M NaC2H3O2 solution. Measure the pH of this solution and record. Save this solution for section 2.4.
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2.4 Calculate the pH of a new solution made by taking 10.0 mL of the solution in 2.3 and diluting it to 45.0 mL with deionized water. Enter this as “theoretical pH” on the report sheet.
Measure out 10.0 mL of the solution in 2.3 with a small graduated cylinder and pour this into a larger graduated cylinder. Add, from your wash bottle, deionized water to the 45 mL level. Mix this solution well and pour this mixture into a clean, dry 50 or 100 mL beaker. Measure the pH of this diluted solution.
2.5 Calculate the pH of a solution made by mixing 3.0 mL of 1.0 M NaC2H3O2 with 18.0 mL of 1.0 M HC2H3O2 . List this as “theoretical pH” on the report sheet.
Measure 18.0 mL of 1.0 M HC2H3O2 that you saved in 2.1 and pour into a clean, dry 50 mL beaker. Then add 3.0 mL of 1.0 M NaC2H3O2 solution and measure the pH. Record this value.
2.6 Place 20.0 mL of 1.0 M HC2H3O2 in your 50 mL beaker. Add 4 drops of methyl orange indicator. Measure the pH and note the color of the solution. Now add about a spoonful of solid NaC2H3O2 and stir to dissolve. Measure the pH again and note the color of this solution.
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