Then, using the freezing-point depression constant for solvent (table 1) and equation (3), you will calculate the molecular weight of the unknown solute sample calculation a solution prepared by dissolving 153 g of an unknown compound in 560 g of naphthalene has a freezing point which is 101 o c lower than the freezing point of pure naphthalene.
Experiment 17 lecture note: i post my lecture notes for these reasons: in case i forgot to mention some crucial points we want to determine the freezing point depression constant for benzophenone, this is the freezing temperature of benzophenone you can compare your value to the known value, 478 ºc o you must make sure to keep. The normal freezing point of cyclohexane is 65 °c and its freezing point depression constant is 202 °c/m what is the molecular formula of the solute solution. Freezing point depression is a colligative property observed in solutions that results from the introduction of solute molecules to a solvent the freezing points of solutions are all lower than that of the pure solvent and is directly proportional to the molality of the solute.
This is the colligative property called freezing point depression the more solute dissolved, the greater the effect an equation has been developed for this behavior it is: δt = i k f m δt is the temperature change from the pure solvent's freezing point to the freezing point of the solution.
Benzophenone freezing point= 499 c benzophenone + unknown freezing point= 430 c benzophenone mass= 5047 g unknown mass= 480 g 1 from the difference between the freezing points of the pure benzophenone and the unknown + benzophenone solution, calculate the freezing point depression of the solution 2. In a more generic way, it is called the molal freezing point depression constant some additional comments about the boiling point and freezing point of a solution pure substances have true boiling points and freezing points, but solutions do not for example, pure water has a boiling point of 100 °c and a freezing point of 0 °c. Freezing point depression is a colligative property observed in solutions that results from the introduction of solute molecules to a solvent benzophenone has a freezing point of 4900 o c.
The freezing point was determined by extrapolating a straight horizontal line from the plot of “temperature vs time” and recording the y-axis value the freezing point of benzophenone was found to be = ° tf 46 1 c compared with the expected value = ° tfactual 47 8 c. 10based on the information for solution 1 and the pure benzophenone, calculate the freezing point depression constant (kf) for benzophenone include the units for the kf value from your calculations kf = _____ b solution 2 1 mass of added benzophenone 5049 g 2. 1) the freezing point of biphenyl (molar mass 154g/mole) is 710 degrees celsius when 1240g of benzophenone (molar mass 182g/mole) is added to 952g of biphenyl the solution is found to freeze at 143 degrees celsius calculate the freezing point depression constant, kf, for biphenyl.
Part two of the experiment, was concerned with determining the freezing point of a benzophenone, cyclohexane solution and adjusting solute concentration to determine its effect on freezing point depression of the solution. T f = (freezing point of pure solvent) - (freezing point of solution) (55 o c) - (28 o c) = 27 o c step 2 : calculate the molal concentration of the solution.
Return to the freezing point depression discussion return to solutions menu problem #11: when 200 grams of an unknown nonelectrolyte compound are dissolved in 5000 grams of benzene, the freezing point of the resulting solution is 377 °c. A solution prepared by dissolving 153 g of an unknown compound in 560 g of naphthalene has a freezing point which is 101 o c lower than the freezing point of pure naphthalene the freezing-point depression constant for naphthalene is 690 o c/m.