Once the solution is completely melted, add the contents of Dish #2 to the test

Question

Once the solution is completely melted, add the contents of Dish #2 to the test tube. The mass of the solute in solution will now be the combined masses of the first and second samples. Repeat the cooling/recording process. Plot the data for each run and determine the freezing points. From each set of data, calculate the molar mass of the unknown solute and average them together. Using the average molar mass and the percent composition of the unknown solute (93.71% C, 6.29% H), determine the empirical formula and the molecular formula of the unknown solute. Calculate mass of cyclohexane using 0.779 g/mL as density. Must show work and record. Dish 1 was 0.25, dish 2 was 0.1463. 20 mL of cyclohexane. Delta Tf=i x m x Kf. Kf is 20.5. Freezing point is pure for cyclohexane is 6.5 C. Thank you and so confused.

Explanation / Answer

Without having delta T values we cant find the molar mass of the unknown solute.

from the given data :

20 ml of cyclohexane === > 15.58 gms

since d = m/v = 0.779

Delta T = i *Kf * m

dish 1 ;

mass of unknown = 0.25 gms

Molality = moles of solute / Mass of solvent in Kg

Molality = 0.25*1000 / 15.58*MW

delta T = 20.5 * 0.25*1000 / 15.58*MW

since delta T values are not given we cant find the molar mass

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