Essay On Freezing Point Experiment

Great Essays
Name: ______________________________________ Date _________________

Lab Partner _________________________________ Section _______________

Objectives: To determine freezing points of pure solvent and solutions using cooling curves. Calculate the freezing point depression for the solutions of unknown. Calculate Molar Mass of unknown solute.

Introduction: When a solute is dissolved in a solvent, the freezing temperature is lowered in proportion to the number of moles of solute added. This property, known as freezing-point depression, is a colligative property; that is, it depends on the ratio of solute and solvent particles, not on the nature of the substance itself. The equation that shows this relationship is
ΔTf = i × Kf × m,
…show more content…
Place the test tube with cyclohexane into the apparatus. Insert thermometer and stirring wire in it. The thermometer should not touch the bottom of the large test tube.
4. Add ice and water into the large beaker. The level of cyclohexane should be lower than the level of ice-water mixture.
5. Stir cycloxehane gently but constantly. Use large stirring rod to stir ice-water mixture constantly. Constant stirring is a key to get good results in this experiment.
6. After the temperature dropped to about 15 oC, start recording the temperature every 15 seconds. Continue recording even after cyclohexane is visually start forming solid ( you will need 5-6 measurements after you see solid in the large test tube.)
7. After you complete this part of the procedure, move large beaker down by releasing the clamps and exposing large test tube with frozen cyclohexane. Do not open the large test tube. Allow the cyclohexane to melt. You will use the same cyclohexane in the next parts of the experiment.
8. After cyclohexane completely melted, immerse the large test tube back into the fresh ice-water mixture by elevating the large beaker and securing it with clamps on the ring
…show more content…
After you complete the second trial, expose the large test tube by lowering the beaker with ice-water mixture. Allow the solid to melt completely. Do not open the large test tube with cyclohexane. You will use the same cyclohexane sample in the next part of the experiment.
Measuring the Freezing Points of the Solutions
11. Measure about 0.4g of the unknown solid solute assigned to your group. Use electronic balance and weighing boat. Do not return excess amount of unknown back to its original container. Dispose in appropriate waste container instead. Record the mass of the unknown solid to the nearest 0.001g.
12. Open the large test tube. Do not remove the thermometer and the stir wire. Transfer the solid from the weighing boat into the cyclohexane, stir well to obtain clear Solution 1. All solid must dissolve, including any on the walls of the large test tube.
13. Close the large test tube, and adjust the thermometer and the stir wire. Immerse the test tube into refreshed the ice-water mixture.
14. Cool the solution to about 15 oC and start recording the temperature in 15 sec intervals. Continue cooling until the solution is frozen and you obtain at least 5 measurements after the appearance of the

Related Documents

  • Decent Essays

    HCl. Keep the solution in ice water bath. Part II: Preparation of the diazonium ion Take 5.5 g of p-toluidine into a 100 mL conical flask and add 8 mL water and 6 mL Conc. HCl to it. Stir the solution and heat it until the solid dissolves.…

    • 2234 Words
    • 9 Pages
    Decent Essays
  • Improved Essays

    Before conducting the experiment, switch on the "MAINS" the Control Unit of Soxtec® Avanti System 2055. Set the appropriate temperature according to the solvent used at 135 ̊C to achieve the level of reflux solvent with 3 to 5 droplets per second. Select the appropriate program specified in the Control Unit to determine the time of boiling (15 minutes), rinsing (30 minutes), recovery (10 minutes) and pre-drying (5 minutes). Open the tap water to allow the reflux process occurred in a condenser at Extraction Unit. With the cooling process by water at about 15 ̊C, the water flow should be adjusted to the rate of 2 L / min to prevent boiling of solvents from the condenser.…

    • 1632 Words
    • 7 Pages
    Improved Essays
  • Decent Essays

    3.4.2.1 Test for milk:- 1. Determination of SNF in milk AIM: - to determine the SNF of milk Apparatus: - lactometer jar, lactometer and thermometer Principle: - It is calculated by using lactometer method. Procedure:-  Warm the milk sample to 40 to 45oCand maintain at this temperature till 5 min.  Mix the contents by rotating and inverting the bottle, taking care to avoid the formation of air bubbles.  Cool the sample to 15.5oC  Invert the sample bottle 2 to 3 times; pour enough milk into the lactometer jar, do not let the air bubbles to form, so that some milk overflows when the lactometer is inserted.…

    • 2449 Words
    • 10 Pages
    Decent Essays
  • Improved Essays

    Camphene Synthesis

    • 1013 Words
    • 5 Pages

    A thermocouple was periodically placed on the outside of the flask to make sure that the mixture did not reach past 50 °C. Once the flask was left to mix for fifteen minutes, a strip of starch-iodide paper was inserted into the mixture to determine whether chlorine (Cl2) was present. The mixture was then left to stir for another fifteen minutes. The flask was then chilled in an ice bath to prepare for filtration. A vacuum filtration apparatus was set up using a 150-mL filter flask and a Büchner funnel.…

    • 1013 Words
    • 5 Pages
    Improved Essays
  • Superior Essays

    Flask Lab Report

    • 907 Words
    • 4 Pages

    Measure and record the exact temperature of the boiling water in the beaker, as well as the barometric pressure in the lab. 12. When the flask has cooled completely, carefully dry the outside of the flask to remove any water. Weigh the flask, foil cover, and vapor with as many sigfigs as possible. 13.…

    • 907 Words
    • 4 Pages
    Superior Essays
  • Improved Essays

    Urea Synthesis Lab Report

    • 988 Words
    • 4 Pages

    This liquid effluent is let down to 27 atm and fed to a special flash-evaporator containing a gas-liquid separator and condenser. Unreacted NH3, CO2 and H2O are thus removed and recycled. An aqueous solution of carbamate-urea is passed to the atmospheric flash drum where further decomposition of carbamate takes place. NH2COONH4 2NH3 + CO2 The pressure is then reduced and a solution of urea dissolved in water and free of other impurities remains. At each stage the unconsumed reactants are absorbed into a water solution which is recycled to the secondary reactor.…

    • 988 Words
    • 4 Pages
    Improved Essays
  • Great Essays

    Then we added 20 mL of DW to the flask and put it into a water bath. We used the stirring rod to stir the mixture up for completely dissolved. If the sample did not dissolve, we put more DW drop by drop using the dropper. When the sample was fully dissolved, we gently put the flask into an ice bath and wait until it recrystallized. We noticed not to move the sample around or it would break the crystals inside.…

    • 1460 Words
    • 6 Pages
    Great Essays
  • Improved Essays

    Iodometry Lab Report

    • 1421 Words
    • 6 Pages

    The addition of H2SO4 will drives off all nitrogen oxide gas that can interfere with the redox reactions. The SO3 vapor that is observed is an indication that all NOx has been driven off. The solution was cooled in ice bath and DI water is added, followed by the addition of NH3 drop wise. The purpose of this step is to create a slightly acidic to neutral solution, which is an ideal condition for the redox reaction as mentioned above. Addition of NH3 will form Cu(NH3)42+,a copper tetramine complex with a dark-blue color, indicating a slightly basic solution.…

    • 1421 Words
    • 6 Pages
    Improved Essays
  • Great Essays

    Procedure: Before beginning each experiment, remove all clutter from the workstation and read the directions for the experiments thoroughly. Part 1: Warm slightly more than 300 mL of water to approximately 70 degrees Celsius. Measure out 150 mL of water into the coffee cup calorimeter. Take the temperature of this water in the coffee cup calorimeter once it has reached a steady temperature. Then, add an ice cube approximately the size of a large marshmallow.…

    • 1006 Words
    • 4 Pages
    Great Essays
  • Improved Essays

    Similarly the crucible and cover were weighed and the difference between the clean crucible and the crucible with sample gave component Y’s mass, and from that the percent composition of the sample of Y. The remaining substance in the test tube was heated to evaporate any remaining solvents. The test tube and solid was measured. This solid ideally should be mainly component Z. However after the third wash with water for component Y, the remaining solid sample seemed to dissolve completely into the water.…

    • 768 Words
    • 4 Pages
    Improved Essays