General Chemistry Lab Experiment 11
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Questions and Answers

What is the primary purpose of using an indicator in titration?

  • To improve the accuracy of the measurements
  • To measure the volume of titrant added
  • To chemically react with the analyte
  • To indicate the end point of the titration (correct)

    • Which of the following statements is true regarding the equivalence point in a titration?

  • It represents the point where moles of titrant equal moles of analyte. (correct)
  • It is always pH 7 for every titration.
  • It occurs before the end point.
  • It can be determined without an indicator.

    • Which indicator would be most appropriate for titrating a weak acid with a strong base?

  • Bromothymol Blue
  • Universal Indicator
  • Phenolphthalein (correct)
  • Methyl Orange

    • How should the burette be prepared before use in a titration?

    <p>Washed with distilled water followed by the titrant solution</p> Signup and view all the answers

    Which of the following characteristics does NOT apply to a primary standard?

    <p>Hygroscopic in nature</p> Signup and view all the answers

    What is the purpose of adding phenolphthalein during the titration process?

    <p>To serve as an indicator for the endpoint of the titration</p> Signup and view all the answers

    How is the normality of the NaOH solution related to the mass of KHP used for the titration?

    <p>The normality is directly proportional to the mass of KHP used.</p> Signup and view all the answers

    If a student uses 0.3 g of KHP instead of 0.274 g, how would this impact the calculated molar concentration of NaOH?

    <p>The molar concentration of NaOH will increase.</p> Signup and view all the answers

    What information is needed to calculate the molar concentration of NaOH using the formula provided?

    <p>Mass of KHP, molar mass of KHP, and volume of NaOH</p> Signup and view all the answers

    Which of the following statements correctly reflects the reaction occurring during the titration?

    <p>KHP forms a salt and water with NaOH.</p> Signup and view all the answers

    Which characteristic distinguishes a primary standard from a secondary standard?

    <p>Primary standards have a precisely known concentration, while secondary standards do not.</p> Signup and view all the answers

    What is a critical requirement for a reaction to qualify for titration?

    <p>The reaction must be stoichiometric.</p> Signup and view all the answers

    Which of the following statements about sodium hydroxide (NaOH) is NOT true?

    <p>NaOH has a low molar mass.</p> Signup and view all the answers

    What is the result of an acid-base titration reaction?

    <p>Salt and water.</p> Signup and view all the answers

    Why are primary standards preferable over secondary standards in standardization?

    <p>Primary standards do not absorb water.</p> Signup and view all the answers

    What is the function of the endpoint in a titration process?

    <p>It indicates the completion of the reaction.</p> Signup and view all the answers

    What type of titration involves the transfer of electrons between species?

    <p>Redox titration.</p> Signup and view all the answers

    Which of the following is a requirement for an effective titration process?

    <p>The reaction must be rapid.</p> Signup and view all the answers

    Study Notes

    General Chemistry Lab: Experiment 11 - Standardization of Sodium Hydroxide Solution

    • Objective: To standardize a solution of NaOH
    • 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.
    • 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.
      • 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.
    • Titration Requirements:
      • Stoichiometric reaction
      • Rapid reaction
      • No side reactions
      • Distinct endpoint (using an indicator)
    • Titration Types:
      • Acid-base Titration (neutralization reaction)
      • Oxidation-Reduction Titration (redox reaction)
      • Gravimetric Titration (precipitation reaction)
    • 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.
    • 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).
    • Volumetric Glassware:
      • Burette, pipette, volumetric flask
    • 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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    Related Documents

    Palestine Polytechnic University General Chemistry Lab Experiment 11 PDF

    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.

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