this is molar mass determination of napthalene by freezing point depression lab

Question

this is molar mass determination of napthalene by freezing point depression lab for chm152

DATA SHEET Determining the mass of the solvent and solute Mass of test tube + beaker M Mass of glass bead M2 Mass of test tube + beaker + benzophenone Mass of test tube + beaker+ glass bead + benzophenone + naphthalene M4 M3 258 .6b Mass of benzophenone-M3 Mi Mass of naphthalene M4 M3-M2 Temperature versus Time data for benzophenone Time sec versus Time data for benzophenone Temp Time Temp Time Temp Time sec 810 840 870 900 930 TempT sec 270 300 330 540 570 600 630 660 690 720 60 90 120 420 I 450 480 510 4a3960 180 990 1020 1050 240 780 Temperature versus Time data for benzophenone & naphthalene Time Temp Time Temp Time Temp Time Temp (sec) CC)(sec) C (sec) CC sec 0 270 .30 154 1300 330 360 390 420 L2.6 450 480 510 540 29. 6 570 600 630 , 660 3 690 720 5-(a 750 780 810 2 840 870 900 930 960 60 120 150 180 210 240 3 990 1020s 2 L 1050 " extend the table as necessary to accommodate time needed for your experiment. Freezing point fo the solvent and solutio Freezing point of benzophenone Freezing point of mixture

Explanation / Answer

Q1) This is because in a cooling curve, the temperature and time are plotted. The temperature is constant during phase changes, thus there are constant temperatures at a varying time interval. However, there are no instances where, there are no instances where there is a constant time interval at varying temperatures. Thus the plot is either curved or platued.

Q2) At the freezing point, solid and liquid phases are present. This is because the liquid is converted to solid at the freezing point.

Q3) Depression of freezing point when an impurity is added is a colligative property. The solution will have a lower freezing point.

Q4) This is because there are two components in the system. First the liquid mixture will cool until it reaches the freezing point of the mixture. Then the component with the higher concentration starts to solidify. Once this going on, the slope of the cooling curve is decreased. Then the mixture hits the eutectic point. All temperature changes are halted and the mixture starts to solidify. Thus there is a temperature range.

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