Chemical Engineering Lab: Sedimentation Study Unit
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Questions and Answers

What is the purpose of stirring the solution in Cylinder 1 until a uniformly distributed solid is achieved?

  • To ensure all particles settle at the same rate
  • To prevent particle aggregation
  • To achieve uniform initial concentration (correct)
  • To increase the settling rate
  • What is the effect of increasing the initial height of suspension on sedimentation rates?

  • Slower sedimentation rates
  • Depends on the type of particles
  • Faster sedimentation rates (correct)
  • No effect on sedimentation rates
  • What is the purpose of recording the height of the clear liquid interface, Z, in the experiment?

  • To measure the initial concentration of particles
  • To calculate the final settling heights, Zf
  • To determine the effect of flocculating agents on sedimentation rates
  • To monitor the settling characteristics of calcium carbonate solutions (correct)
  • What is the role of flocculating agents in sedimentation?

    <p>To enhance particle aggregation and increase settling rates</p> Signup and view all the answers

    What is the purpose of plotting the height of the clear liquid interface, Z, versus settling time, t?

    <p>To compare the settling characteristics of different cylinders</p> Signup and view all the answers

    Why is it recommended to run all five cylinders simultaneously?

    <p>To reduce the experiment duration</p> Signup and view all the answers

    What is the primary factor that determines the separation of settleable solids from water?

    <p>Size and type of particles</p> Signup and view all the answers

    Which type of particles can be removed easily from water due to their density?

    <p>Sand or silt</p> Signup and view all the answers

    What is the purpose of adding a chemical, such as an iron salt or aluminum sulfate, to water in sedimentation?

    <p>To coagulate and flocculate colloidal material</p> Signup and view all the answers

    What happens to particles with the same electrical charge in sedimentation?

    <p>They repel each other</p> Signup and view all the answers

    What is the primary purpose of sedimentation in water treatment?

    <p>To let suspended material settle by gravity</p> Signup and view all the answers

    What is the primary objective of Experiment B in this laboratory?

    <p>To study the effect of flocculating agents on sedimentation rates</p> Signup and view all the answers

    What affects the settling characteristics of calcium carbonate solutions?

    <p>All of the above</p> Signup and view all the answers

    What is the common initial concentration of calcium carbonate used in all the cylinders in Experiment B?

    <p>100 g of calcium carbonate in 2 L of water</p> Signup and view all the answers

    What is the role of flocculating agents in sedimentation?

    <p>To coagulate and flocculate colloidal material</p> Signup and view all the answers

    What is the purpose of decreasing the velocity of the water-flow channel in sedimentation?

    <p>To allow particles to settle by gravity</p> Signup and view all the answers

    What is the effect of increasing the initial suspension height on the sedimentation rate?

    <p>It increases the sedimentation rate</p> Signup and view all the answers

    What is the primary objective of comparing the curves for cylinders 2, 4, and 5?

    <p>To study the effect of initial suspension heights on sedimentation rates</p> Signup and view all the answers

    What is the primary factor that affects the sedimentation rates in the comparison of cylinders 1, 2, and 3?

    <p>Flocculant volumes</p> Signup and view all the answers

    What is the primary factor that affects the sedimentation rates in the comparison of cylinders 1, 2, and 3 in Experiment B?

    <p>Flocculant volumes</p> Signup and view all the answers

    What is the purpose of using different volumes of flocculant in Experiment B?

    <p>To study the effect of flocculating agents on sedimentation rates</p> Signup and view all the answers

    What is the common initial suspension height (Z0) used in all the cylinders in Experiment B?

    <p>90 cm</p> Signup and view all the answers

    Study Notes

    Sedimentation Study Unit: Rate of Sedimentation of Calcium Carbonate in Water

    • Sedimentation is the process of letting suspended material settle by gravity
    • Factors affecting sedimentation:
      • Size and type of particles
      • Velocity of water flow
      • Shape of particles
      • Electrical charge of particles
    • Sedimentation tank operation:
      • Decreasing water velocity to below 1 ft/s to remove particles
      • Gravel and grit removed easily, but colloidal material requires coagulation and flocculation

    Experiment Procedure

    • Stir the solution in each cylinder to achieve a uniformly distributed solids
    • Record initial time, t0, and height of clear liquid interface, Z0
    • Record Z every 5 minutes until settling stops
    • Repeat for all five cylinders
    • Plot Z vs. settling time, t

    Effects of Flocculating Agents and Initial Concentrations

    • Five cylinders with different flocculant concentrations: 5 ml, 10 ml, 15 ml, 20 ml, and 25 ml
    • Effects of flocculating agents on sedimentation rates:
      • Compare curves for cylinders 1 to 5
    • Effects of initial concentrations on sedimentation rates:
      • Compare curves for cylinders 1, 2, and 3
    • Effects of initial suspension heights on sedimentation rates:
      • Compare curves for cylinders 2, 4, and 5

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    Description

    This quiz covers a laboratory experiment on sedimentation, focusing on the rate of sedimentation of calcium carbonate in water. It explores the process of letting suspended material settle by gravity.

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