15 Questions
What is the main purpose of potentiometric titration?
To determine the concentration of an unknown analyte without using a chemical indicator
What does pH measure in a solution?
The concentration of hydrogen ions
Why is potentiometric titration considered more reliable than titrations using chemical indicators?
It does not rely on visual color changes in the solution
What is the volume of NaOH used at the end point in the procedure?
The volume at which the solution changes to pink
What type of titration is potentiometric titration classified as?
Acid-base titrations (neutralization titrations)
What is the purpose of washing the electrode with D. W. and drying it before immersing it in the buffer solutions?
To ensure accurate pH measurements by removing any impurities on the electrode surface
In the titration process, why is it important to add smaller volumes of NaOH towards the equivalence point?
To achieve a more precise determination of the equivalence point
Why is the shape of the graph between pH and volumes of NaOH typically like shape (A)?
It represents the characteristic S-shaped curve of a titration involving a strong acid and a strong base
What is the main reason behind considering HCl a strong acid?
HCl dissociates completely into ions in aqueous solution
Why is it important to record the values of pH for the mixture in the beaker after each addition of NaOH during titration?
To monitor the progress of the reaction and identify the equivalence point
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?
To calibrate the pH meter and ensure accurate pH measurements
Why is it recommended to add larger volumes of NaOH towards the end of the titration, just before the pH stops rising markedly?
To accurately determine the endpoint of the titration
What does the plot of pH against volumes of NaOH look like during the titration process according to the text?
An initial increase, then a plateau, and finally a steep increase
Why is HCl considered a strong acid?
It completely dissociates into ions in solution
How can the molarity of the HCl solution be calculated from the titration data?
By finding the volume of NaOH at the equivalence point
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.
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.
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