The relative error can be reduced If a more precise thermometer is used. Assume
ID: 1068807 • Letter: T
Question
The relative error can be reduced If a more precise thermometer is used. Assume that with the more precise thermometer you can determine the temperature to within plusminus 0.02 degree C. If the measured freezing-point depression with such a thermometer is 9.52 degree C, what molality is determined for this solution? What is the relative error in the molality as determined with this more precise thermometer? Cyclohexanol, C_6H_11 OH, is sometimes used as the solvent in molecular weight determinations by freezing point depression. If 0.253 g of benzoic acid. C_6H_5COOH, dissolved in 12.45 g of cyclohexanol, lowered the freezing point of pure cyclohexanol by 6.55 degree C. what Is the molal freezing-point constant of this solvent?Explanation / Answer
2.
a. molality = dTf/iKf
= 9.52/1 x 1.86
= 5.12 m
This calculation is done for aqueus solution.
% relative error in molality = 0.002%
1. molalrity of solution = 0.253/100.16 x 0.01245 = 0.203 m
Kf = dTf/i.m
= 6.55/1 x 0.203
= 32.266 oC/m