Data Volume of cyclohexane200 mL Mass of cyalohexane SDS6 k

. Data Volume of cyclohexane:20.0 mL Mass of cyalohexane: S-DS6 k Mass of unknown substance: samplo 1: 02 saple 2:37 2 2. F xane and solutions t of T,of cyclohexane (C) 1 trial T of solutions (C) Sample 1Sample 1+2 Time (sec) 2d trial 0.2 \' S. 140 S. 41.3 6-2 2 -19-

Solution

a-No difference. Freezing point of a pure substance will not change because it is a chemicalproperty of the compound. Since it is pure cyclohexane there is no solute.

b)-The solute concentration increases because there is less solvent in the solution. Since the soluteconcentration increases then the vapor pressure will lower, also it will increase the boiling pointand freezing point will experience a depression (deltaT will increase) compared to the solutionbefore evaporation occurred. If the loss of cyclohexane is not taken into account into thecalculation then the molar mass will be smaller then what is should be

c)-may be it is due to some freezing of the sample that some powder left on paper

d)-A colligative property is dependent on the amount of dissolved solute not its chemical identity.So one should combine the foreign solute and any additional solutes placed in the cyclohexaneto get the correct calculations. However, if one did not know about the additional solute and stillcalculated the molar mass without taking into account the added solute one would find that thechange in temperature would increase and the molar mass would be once again smaller thenwhat it should be.

e)-No Effect. You are measuring the change in temperature.

f)-The effect of a solute on the freezing point of a solvent. The freezing-point depression is proportional to the molal concentration of the solute.