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May 15
To calculate the pH using titration, you will need to know the volume of the titrant added to the solution being titrated, as well as the concentration of the titrant and the initial concentration of the solution being titrated.
1. Determine the moles of titrant added to the solution by multiplying the volume of titrant added by its concentration.
2. Determine the moles of the analyte (the substance being titrated) by using the stoichiometry of the reaction between the titrant and the analyte.
3. Calculate the concentration of the analyte in the solution after the titration by dividing the moles of analyte by the total volume of the solution.
4. Use the concentration of the analyte to calculate the pH of the solution using the formula for the pH of a weak acid or base, depending on the nature of the analyte.
5. If the analyte is a weak acid or base, you may need to use the Henderson-Hasselbalch equation to calculate the pH.
It is important to note that the pH calculation may be more complex if the titration involves a polyprotic acid or base, or if there are multiple equilibria involved in the reaction. In these cases, additional calculations and considerations may be necessary to accurately determine the pH of the solution.
1. Determine the moles of titrant added to the solution by multiplying the volume of titrant added by its concentration.
2. Determine the moles of the analyte (the substance being titrated) by using the stoichiometry of the reaction between the titrant and the analyte.
3. Calculate the concentration of the analyte in the solution after the titration by dividing the moles of analyte by the total volume of the solution.
4. Use the concentration of the analyte to calculate the pH of the solution using the formula for the pH of a weak acid or base, depending on the nature of the analyte.
5. If the analyte is a weak acid or base, you may need to use the Henderson-Hasselbalch equation to calculate the pH.
It is important to note that the pH calculation may be more complex if the titration involves a polyprotic acid or base, or if there are multiple equilibria involved in the reaction. In these cases, additional calculations and considerations may be necessary to accurately determine the pH of the solution.
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Google Gemini AI
May 15
Materials:
- Burette
- Pipette
- Erlenmeyer flask
- Phenolphthalein indicator
- Known concentration of NaOH solution
- Unknown acidic solution
Procedure:
1. Prepare the solution to be titrated:
- Pipette a known volume of the unknown acidic solution into an Erlenmeyer flask.
2. Add the indicator:
- Add a few drops of phenolphthalein indicator to the solution. The solution will remain colorless.
3. Titrate the solution:
- Fill a burette with the known NaOH solution.
- Slowly add NaOH solution dropwise to the acidic solution while swirling constantly.
4. Observe the color change:
- As NaOH is added, the solution will gradually turn pink.
- Continue adding NaOH until the solution turns a faint but permanent pink color.
5. Record the volume of NaOH used:
- Note the initial and final volume readings on the burette to determine the volume of NaOH used in the titration.
Calculations:
1. Calculate the number of moles of NaOH used:
- Moles of NaOH = Concentration of NaOH (M) x Volume of NaOH used (mL)
2. Calculate the number of moles of acid present:
- Moles of acid = Moles of NaOH used
3. Calculate the concentration of the acid:
- Concentration of acid (M) = Moles of acid / Volume of acidic solution (mL)
4. Calculate the pH of the solution:
- pH = -log[H+]
- [H+] = Concentration of acid (M) x Dissociation constant (Ka) for the acid
Example:
Let's say we titrated 20.0 mL of an unknown acidic solution with 15.0 mL of 0.100 M NaOH solution, and the acid has a Ka of 1.0 x 10^-5.
1. Moles of NaOH used = 0.100 M x 0.015 L = 0.0015 moles
2. Moles of acid = 0.0015 moles
3. Concentration of acid = 0.0015 moles / 0.020 L = 0.075 M
4. pH = -log(0.075 M x 1.0 x 10^-5) = -log(7.5 x 10^-7) = 3.12
Therefore, the pH of the unknown acidic solution is 3.12.
- Burette
- Pipette
- Erlenmeyer flask
- Phenolphthalein indicator
- Known concentration of NaOH solution
- Unknown acidic solution
Procedure:
1. Prepare the solution to be titrated:
- Pipette a known volume of the unknown acidic solution into an Erlenmeyer flask.
2. Add the indicator:
- Add a few drops of phenolphthalein indicator to the solution. The solution will remain colorless.
3. Titrate the solution:
- Fill a burette with the known NaOH solution.
- Slowly add NaOH solution dropwise to the acidic solution while swirling constantly.
4. Observe the color change:
- As NaOH is added, the solution will gradually turn pink.
- Continue adding NaOH until the solution turns a faint but permanent pink color.
5. Record the volume of NaOH used:
- Note the initial and final volume readings on the burette to determine the volume of NaOH used in the titration.
Calculations:
1. Calculate the number of moles of NaOH used:
- Moles of NaOH = Concentration of NaOH (M) x Volume of NaOH used (mL)
2. Calculate the number of moles of acid present:
- Moles of acid = Moles of NaOH used
3. Calculate the concentration of the acid:
- Concentration of acid (M) = Moles of acid / Volume of acidic solution (mL)
4. Calculate the pH of the solution:
- pH = -log[H+]
- [H+] = Concentration of acid (M) x Dissociation constant (Ka) for the acid
Example:
Let's say we titrated 20.0 mL of an unknown acidic solution with 15.0 mL of 0.100 M NaOH solution, and the acid has a Ka of 1.0 x 10^-5.
1. Moles of NaOH used = 0.100 M x 0.015 L = 0.0015 moles
2. Moles of acid = 0.0015 moles
3. Concentration of acid = 0.0015 moles / 0.020 L = 0.075 M
4. pH = -log(0.075 M x 1.0 x 10^-5) = -log(7.5 x 10^-7) = 3.12
Therefore, the pH of the unknown acidic solution is 3.12.
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