COLLIGATIVE PROPERTIES

1. I need help with the standard deviation/percentage error in the attached lab experiement.

2. Also need help graphing for the ethyl acelate and unknown solvent -- plotting negative delta T versus the total volume of solute that was added (2 graphs) and calculation of the slopes

3.  I am not certain but I believe this question relates to the accepted value of the freezing point of cyclohexane 6.5 degrees and a Kf of 20.0 (not the 8.0 degrees that was found in the lab).  Can an answer to the following question be determined using this assumption?  Relationship of freezing point depression constant to its enthalpy of fusion and its entropy of fusion with the following formulas

delta H fus = MRT(squared)
                   ____________

                    1000Kf

and delta S fus = MRT of cyclohexane
                       ____________

                       1000 Kf

t is the freezing point of pure cyclohexane and R is the gas constant.  Units need to be arranged so that delta H comes out in KJ mol-1 and delta s comes out in JK-1 mol-1.  

Please help me as I am totally confused.  Thank you!