The freezing point depression of a solution of nitrobenzene and a nonionic

# The freezing point depression of a solution of

This preview shows page 5 - 15 out of 17 pages.

2.The freezing point depression of a solution of nitrobenzene and a nonionic unknown was used to determine the molar mass of the unknown. Time-temperature data for the cooling of nitrobenzene and for the cooling of a solution containing 50.0 g of nitrobenzene and 5.00 mL of a nonionic liquid unknown are given below the density of the unknown was 0.714 g/mL^-1. The Kf of nitrobenzene is 6.87 kg/ mol ^-1.
a.Determine the freezing point of nitrobenzene from the curve. b.Determine the freezing point of the unknown solution-0.90 c.Determine the freezing point depression, ΔTfΔt= Tf-ΔTfΔt=(5.25°C-(-0.90°C)) d.Calculate the molality of the solution, mc. e.Calculate the gram molar mass of the unknown. 3.Briefly explain why it is absolutely critical the the test tube containing the sample of nitrobenzene be absolutely dry when determining the freezing temperature of nitrobenzene.
Choice 1. Data sheet 1 Time, sec First Temp, ° C Second Temp, ° C 0 22.9 ° C 24.3 ° C 15 22.7 ° C 25.4 ° C 30 22.0 ° C 25.5 ° C 45 21.5 ° C 24.7 ° C 60 21.2 ° C 23.8 ° C 75 20.9 ° C 23.1 ° C 90 20.7 ° C 22.7 ° C 105 20.5 ° C 22.3 ° C 120 20.3 ° C 21.9 ° C 135 20.2 ° C 21.4 ° C 150 20.5 ° C 21.2 ° C 165 21.0 ° C 21.0 ° C 180 21.1 ° C 20.8 ° C 195 21.1 ° C 20.7 ° C 210 21.1 ° C 20.5 ° C 225 21.1 ° C 20.4 ° C 240 21.1 ° C 20.3 ° C 255 21.1 ° C 20.2 ° C 270 21.1 ° C 20.1 ° C
285 21.1 ° C 20.4 ° C 300 21.1 ° C 20.8 ° C 315 20.9 ° C 21.0 ° C 330 20.9 ° C 21.0 ° C 345 20.9 ° C 21.0 ° C 360 20.9 ° C 21.0 ° C 375 21.0 ° C 390 21.0 ° C 405 20.9 ° C 420 20.8 ° C 435 20.7 ° C 450 20.8 ° C 465 20.8 ° C
Choice 2. Data sheet 2 Time, sec First Temp, °C Second Temp, °C 0 22.7°C 24.3 °C 15 24.3°C 23.9 °C 30 24.9°C 22.8 °C 45 24.3°C 22.1 °C 60 22.5°C 21.8 °C 75 22.3°C 20.5 °C 90 21.4°C 20.1 °C 105 20.9°C 19.2 °C 120 20.3°C 19.0 °C
135 20.1°C 18.7 °C 150 19.7°C 18.4 °C 165 19.5°C 18.5 °C 180 19.4°C 18.9 °C 195 19.2 °C 18.9 °C 210 19.0 °C 18.9 °C 225 18.7 °C 19.0 °C 240 18.6 °C 19.0 °C 255 18.4 °C 18.9 °C 270 18.4 °C 18.8 °C 285 18.4 °C 18.7 °C 300 18.9 °C 18.6 °C 315 19.1 °C 18.4 °C 330 19.1 °C 18.4 °C 345 19.2 °C 18.3 °C 360 19.2 °C 18.1 °C 375 19.1 °C 18.2 °C 390 19.1 °C 18.2 °C 405 19.1 °C 18.2 °C 420 19.0 °C 18.1 °C 435 18.9 °C 18.2 °C 445 18.8 °C 18.1 °C 465 18.9 °C 18.1 °C
Choice 3. Data sheet 3 Time, sec First Temp, °C Second Temp, °C 0 16.5 °C 19.4 °C 15 15.8 °C 19.3 °C 30 15.4 °C 18.5 °C 45 15.0 °C 17.6 °C 60 14.8 °C 16.7 °C 75 14.5 °C 16.3 °C 90 14.4 °C 16.0 °C 105 14.5 °C 15.6 °C 120 14.6 °C 15.2 °C
135 14.8 °C 15.0 °C 150 14.7 °C 14.8 °C 165 14.7 °C 14.5 °C 180 14.6 °C 14.5 °C 195 14.6 °C 14.6 °C 210 14.4 °C 14.6 °C 225 14.7 °C 240 14.8 °C 255 14.6 °C 270 14.6 °C 285 14.6 °C 300 14.5 °C 315 14.4 °C 330 14.3 °C 345 14.4 °C 360 14.4 °C 375 14.4 °C 390 14.4 °C
Data sheet 4 1. Determining the freezing temperature of the t-Butyl alcohol Mass of t-Butyl alcohol, test tube and flask, (grams): 168.7g Mass of test tube and flask, (grams): 150.4g Mass of t-Butyl alcohol, (grams): 18.3g

#### You've reached the end of your free preview.

Want to read all 17 pages?

• Fall '12