Biology Prep: pH and Titration
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Questions and Answers

What is the expected color change when the endpoint of the titration is reached?

  • Pink (correct)
  • Green
  • Blue
  • Yellow
  • What unit is used to express molarity?

  • liters/mole
  • grams/liter
  • moles/liter (correct)
  • moles/grams
  • The same titrant is used to titrate both the 0.02 M and 0.04 M HCl solutions.

    True

    How many 100 µl drops of titrant were required to reach the endpoint for the 0.02 M HCl + phenol red solution?

    <p>19</p> Signup and view all the answers

    A mole is defined as 6.02 x 10^23 units of any substance.

    <p>True</p> Signup and view all the answers

    What is the significance of maintaining optimal concentrations of hydrogen ions (H+) in body fluids?

    <p>It is essential for the proper function of proteins and biological molecules.</p> Signup and view all the answers

    The total volume of titrant required to reach the endpoint for the 0.02 M HCl + phenol red solution is _____ µl.

    <p>1900</p> Signup and view all the answers

    Match the following components to their respective values based on the titration data:

    <p>0.02 M HCl + phenol red = 19 drops 0.04 M HCl + phenol red = 40 drops Total volume for 0.02 M = 1900 µl Total volume for 0.04 M = 4000 µl</p> Signup and view all the answers

    Molarity is calculated using the formula Molarity = moles of solute divided by ________.

    <p>liter of solution</p> Signup and view all the answers

    Match the following terms with their correct descriptions:

    <p>Molarity = Concentration of solute in a solution Mole = 6.02 x 10^23 units Aqueous solution = Water as a solvent pH = Measure of hydrogen ion concentration</p> Signup and view all the answers

    Study Notes

    Molarity and Solutions

    • Molarity indicates solute concentration in a solution, expressed as moles of solute per liter of solution (M).
    • A mole corresponds to approximately 6.02 x 10^23 units, such as atoms or molecules.
    • Importance of maintaining optimal hydrogen ion (H+) concentration in body fluids for cell function.

    Titration Process

    • Titration is a technique to determine the concentration of a solution by adding a titrant until a reaction endpoint is reached.
    • In this exercise, two hydrochloric acid (HCl) solutions (0.02 M and 0.04 M) are used with phenol red as an indicator.

    Experimental Setup

    • Label test tubes for 0.02 M and 0.04 M HCl solutions, measure 5 mL of each, and add phenol red.
    • Titration involves adding a base to neutralize HCl; expected color change to pink indicates the endpoint.

    Titration Observations

    • 0.02 M HCl required 19 drops of titrant (1900 µL) to achieve a color change to pink.
    • 0.04 M HCl required 40 drops (4000 µL), confirming that higher concentration requires more titrant for neutralization.
    • Strong correlation between HCl concentration and the volume of titrant needed.

    Experimental Protocol for Titration of Body Fluids

    • Use test tubes labeled for each body fluid type: saliva, gastric juice, pancreatin, and urine.
    • Measure and mix each body fluid with phenol red, noting initial colors.
    • Choose appropriate titrant (HCl or NaOH) based on initial color, record the number of drops required to neutralize.

    Results and Analysis of Body Fluids

    • Average titration data includes:

      • Saliva: 1 drop (100 µL)
      • Gastric Juice: 16 drops (1600 µL)
      • Pancreatin: 5 drops (500 µL)
      • Urine: 4 drops (400 µL)
    • Gastric juice identified as most acidic, requiring the greatest titrant volume.

    • Pancreatin judged as most basic, indicated by bright pink color upon phenol red addition.

    • Saliva deemed closest to neutral, needing the least amount of titrant.

    pH Test Results

    • Saliva has a pH of 7 (neutral).
    • Gastric juice has a low pH of 2 (highly acidic).
    • Pancreatin has a high pH of 9 (basic).
    • Urine has a pH of 6 (slightly acidic).

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    Description

    This quiz covers essential concepts in biology related to pH and titration techniques. You'll learn about molarity, the pH scale, and the use of indicators in titrations. Prepare for your pre-health professions coursework with practical applications of these concepts.

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