# Colligative Properties Problem Set

This problem set was developed by S.E. Van Bramer for Chemistry 145 at Widener University.

 Compound Formula Density (20 °C, g cm-3) FP (°C) BP (°C) Kf (°C m-1) Kb (°C m-1) Vap P (25 °C, Pa) Acetic Acid CH3COOH 1.0492 16.6 117.9 3.90 3.07 2.11*103 Benzene C6H6 0.8765 5.5 80.1 4.90 2.53 1.261*104 Carbon Tetrachloride CCl4 1.5940 -22.99 76.54 2.98 5.03 1.541*104 Nitrobenzene C6H5NO2 1.2037 5.7 210.8 7.00 5.24 55.1 Water H2O 0.998203 0.000 100.0 1.86 0.512 3.467*103 Ethanol C2H6O 0.7893 -117.3 78.5 1.22 7900

1. For a mixture prepared by combining 200.0 mL of nitrobenzene and 1.00 L of water.
1. Calculate the mole fraction of each compound in the mixture
2. Calculate the vapor pressure of each compound in the mixture
3. Calculate the total vapor pressure of the mixture

2. For a mixture prepared by mixing 5.00 g of caffeine (C8H10N4O2) with 250.0 mL of water. The final density of this mixture is 1.05 g mL-1.
1. Calculate the boiling point of this mixture
2. Calculate the vapor pressure of this mixture
3. Calculate the freezing point of this mixture
4. Calculate the osmotic pressure of this mixture at 25 °C.

3. For a mixture prepared by mixing 10.0 g of sodium sulfate in 250 mL of water. The final density of this mixture is 1.10 g mL-1.
1. Calculate the boiling point of this mixture
2. Calculate the vapor pressure of this mixture
3. Calculate the freezing point of this mixture
4. Calculate the osmotic pressure of this mixture

4. You are examining forensics data for a court case and need to identify an anelgesic (pain killer). It could be either acetylsalicylic acid (asprin), ibuprofen (advil) or acetaminophen (tylenol). A mixture of the unknown is prepared by mixing 10.0 grams of unknown and diluting to 250 mL with ethanol. The density of this solution is 0.80 g mL-1. Identify the unknown based upon the following:
1. The boiling point of this mixture is 78.8 °C.
2. The osmotic pressure of this mixture is 480400 Pa at 25 °C.

Please send comments or suggestions to svanbram@science.widener.edu

Scott Van Bramer
Department of Chemistry
Widener University
Chester, PA 19013