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Questions and Answers
What is the primary purpose of using an indicator in titration?
What is the primary purpose of using an indicator in titration?
Which of the following statements is true regarding the equivalence point in a titration?
Which of the following statements is true regarding the equivalence point in a titration?
Which indicator would be most appropriate for titrating a weak acid with a strong base?
Which indicator would be most appropriate for titrating a weak acid with a strong base?
How should the burette be prepared before use in a titration?
How should the burette be prepared before use in a titration?
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Which of the following characteristics does NOT apply to a primary standard?
Which of the following characteristics does NOT apply to a primary standard?
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What is the purpose of adding phenolphthalein during the titration process?
What is the purpose of adding phenolphthalein during the titration process?
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How is the normality of the NaOH solution related to the mass of KHP used for the titration?
How is the normality of the NaOH solution related to the mass of KHP used for the titration?
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If a student uses 0.3 g of KHP instead of 0.274 g, how would this impact the calculated molar concentration of NaOH?
If a student uses 0.3 g of KHP instead of 0.274 g, how would this impact the calculated molar concentration of NaOH?
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What information is needed to calculate the molar concentration of NaOH using the formula provided?
What information is needed to calculate the molar concentration of NaOH using the formula provided?
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Which of the following statements correctly reflects the reaction occurring during the titration?
Which of the following statements correctly reflects the reaction occurring during the titration?
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Which characteristic distinguishes a primary standard from a secondary standard?
Which characteristic distinguishes a primary standard from a secondary standard?
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What is a critical requirement for a reaction to qualify for titration?
What is a critical requirement for a reaction to qualify for titration?
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Which of the following statements about sodium hydroxide (NaOH) is NOT true?
Which of the following statements about sodium hydroxide (NaOH) is NOT true?
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What is the result of an acid-base titration reaction?
What is the result of an acid-base titration reaction?
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Why are primary standards preferable over secondary standards in standardization?
Why are primary standards preferable over secondary standards in standardization?
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What is the function of the endpoint in a titration process?
What is the function of the endpoint in a titration process?
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What type of titration involves the transfer of electrons between species?
What type of titration involves the transfer of electrons between species?
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Which of the following is a requirement for an effective titration process?
Which of the following is a requirement for an effective titration process?
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Study Notes
General Chemistry Lab: Experiment 11 - Standardization of Sodium Hydroxide Solution
- Objective: To standardize a solution of NaOH
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Introduction:
- A standard solution is a solution with a precisely known concentration.
- It's used to determine the concentration of other solutions through titration.
- Titration is a process where one solution (titrant) is slowly added to another (analyte) until a reaction endpoint is reached. This endpoint involves a color change using an indicator.
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Standard Solution Types:
- Primary Standard: Highly pure, stable, not hygroscopic, high molar mass, crystalline compounds (e.g., KIO₃, Na₂CO₃, KHP). Primarily used for the preparation of accurate concentration solutions.
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Secondary Standard: Does not have the properties of a primary standard and must be standardized using a primary standard (e.g., NaOH, HCl)
- NaOH reacts with glass and CO₂, absorbs water.
- HCl evaporates, not stable.
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Titration Requirements:
- Stoichiometric reaction
- Rapid reaction
- No side reactions
- Distinct endpoint (using an indicator)
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Titration Types:
- Acid-base Titration (neutralization reaction)
- Oxidation-Reduction Titration (redox reaction)
- Gravimetric Titration (precipitation reaction)
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Acid-Base Titration:
- Acid + Base → Salt + Water
- Equivalent point (stoichiometric point): The point where reactants are present in stoichiometric ratios.
- Endpoint is when an indicator shows a change in color. Equivalent and endpoint are usually close but not always the same.
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Indicator:
- A dye that changes color in acidic and basic media.
- The color change occurs at or near the endpoint.
- It's a weak organic acid or base that changes color when protonated or deprotonated.
- Chosen according to the pH at the endpoint (e.g., phenolphthalein changes color at pH 8-8.2).
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Volumetric Glassware:
- Burette, pipette, volumetric flask
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Procedure:
- Wash burette with distilled water.
- Rinse burette with the 0.1 M NaOH solution, then fill with the solution.
- Ensure the tip of the burette is filled with the solution.
- Weigh a known amount of KHP.
Procedure (continued)
- Add the weighed KHP to a flask with 30 ml of water.
- Heat to dissolve the KHP.
- Add 1-2 drops of phenolphthalein indicator.
- Slowly add NaOH solution to the KHP solution from the burette until the color changes to a faint pink.
- Note the volume of NaOH used at the endpoint.
- Calculate the molar concentration of the NaOH solution.
Calculations
- The balanced chemical reaction equation is required to calculate molar concentration.
- The mass of KHP is known.
- The volume of NaOH needed is measured from the burette.
- Using the balanced chemical equation and the known measurements, the molar concentration of NaOH can be calculated.
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Description
Explore the standardization of sodium hydroxide solution in this chemistry lab quiz. Understand the importance of primary and secondary standards in titration processes and the characteristics of standard solutions. Test your knowledge on key concepts to ensure accurate concentration measurements.
