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Questions and Answers
What is the main purpose of potentiometric titration?
What is the main purpose of potentiometric titration?
- To classify different types of titrations based on their methods
- To determine the concentration of an unknown analyte without using a chemical indicator (correct)
- To measure the pH of a solution using a chemical indicator
- To detect the presence of unsuspected species in a solution
What does pH measure in a solution?
What does pH measure in a solution?
- The concentration of hydroxide ions
- The negative logarithm of the activity of hydrogen ions
- The activity of oxygen ions
- The concentration of hydrogen ions (correct)
Why is potentiometric titration considered more reliable than titrations using chemical indicators?
Why is potentiometric titration considered more reliable than titrations using chemical indicators?
- It can be used with colored or turbid solutions
- It measures the electric potential across the substance
- It does not rely on visual color changes in the solution (correct)
- It can detect the presence of unsuspected species
What is the volume of NaOH used at the end point in the procedure?
What is the volume of NaOH used at the end point in the procedure?
What type of titration is potentiometric titration classified as?
What type of titration is potentiometric titration classified as?
What is the purpose of washing the electrode with D. W. and drying it before immersing it in the buffer solutions?
What is the purpose of washing the electrode with D. W. and drying it before immersing it in the buffer solutions?
In the titration process, why is it important to add smaller volumes of NaOH towards the equivalence point?
In the titration process, why is it important to add smaller volumes of NaOH towards the equivalence point?
Why is the shape of the graph between pH and volumes of NaOH typically like shape (A)?
Why is the shape of the graph between pH and volumes of NaOH typically like shape (A)?
What is the main reason behind considering HCl a strong acid?
What is the main reason behind considering HCl a strong acid?
Why is it important to record the values of pH for the mixture in the beaker after each addition of NaOH during titration?
Why is it important to record the values of pH for the mixture in the beaker after each addition of NaOH during titration?
What is the purpose of immersing the electrode in buffer solutions with pH 4 and pH 9 before recording the pH value of the HCl solution?
What is the purpose of immersing the electrode in buffer solutions with pH 4 and pH 9 before recording the pH value of the HCl solution?
Why is it recommended to add larger volumes of NaOH towards the end of the titration, just before the pH stops rising markedly?
Why is it recommended to add larger volumes of NaOH towards the end of the titration, just before the pH stops rising markedly?
What does the plot of pH against volumes of NaOH look like during the titration process according to the text?
What does the plot of pH against volumes of NaOH look like during the titration process according to the text?
Why is HCl considered a strong acid?
Why is HCl considered a strong acid?
How can the molarity of the HCl solution be calculated from the titration data?
How can the molarity of the HCl solution be calculated from the titration data?
Study Notes
Potentiometric Titration
- The main purpose of potentiometric titration is to determine the concentration of a solution (e.g., HCl) by measuring the potential (voltage) of a reaction between the solution and a titrant (e.g., NaOH).
- pH measures the concentration of hydrogen ions (H+) in a solution.
Advantages of Potentiometric Titration
- Potentiometric titration is considered more reliable than titrations using chemical indicators because it provides a more accurate and precise measurement of the endpoint.
Titration Procedure
- The volume of NaOH used at the end point is the volume at which the pH of the solution sharply increases, indicating the equivalence point.
- Potentiometric titration is classified as a type of volumetric titration.
Electrode Preparation
- The electrode should be washed with distilled water (D.W.) and dried before immersing it in the buffer solutions to ensure accurate pH measurements.
Titration Process
- Smaller volumes of NaOH should be added towards the equivalence point to accurately determine the endpoint.
- The graph of pH against volumes of NaOH typically has an S-shape (A) due to the rapid change in pH at the equivalence point.
Acid-Base Properties
- HCl is considered a strong acid because it completely dissociates in water, resulting in a high concentration of hydrogen ions (H+).
pH Measurement
- Recording the pH values of the mixture after each addition of NaOH during titration is important to track the progress of the reaction and determine the endpoint.
- The electrode should be calibrated by immersing it in buffer solutions with pH 4 and pH 9 before recording the pH value of the HCl solution to ensure accurate pH measurements.
Titration Data Analysis
- The plot of pH against volumes of NaOH during the titration process typically shows a sharp increase in pH at the equivalence point.
- The molarity of the HCl solution can be calculated from the titration data by using the volume of NaOH at the equivalence point and the stoichiometry of the reaction.
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Description
Learn about the laboratory method of potentiometric titration to determine the concentration of an unknown analyte without using a chemical indicator. Understand how pH or electric potential measurements are used to determine the equivalent point in the process.
