CHM 2046C Sample Exam Answers

Module Eight Part II: Solutions Chapter 14

Part R: Colligative Properties: Raoult’s Law 4 point

A 55 gram sample of ethylene glycol HOCH₂CH₂OH , is dissolved in 500.0 g of water.

The vapor pressure of water at 32 ^oC is 35.7 mm Hg. What is the vapor pressure of the

water-ethylene glycol solution at 32 ^oC? (Ethylene Glycol is nonvolatile.)

55 g EG solute		1 mol EG solute
---------------	X	--------------	=	0.89 mol EG solute
1		62 g EG solute

500 g H2O		1 mol H2O
---------------	X	--------------	=	27.78 mol H2O Solvent
1		18 g H2O

Total Mole_solution = 0.89 mol _{EG solute} + 27.78 mol _{H2O solvent} = 28.67 mol

		27.78 mol H2O Solvent
Χsolvent	=	--------------	=	0.969
		28.67 mol solution

P_solvent = Χ_solvent P^o_{pure solvent}

Answer:

P_solvent =( 0.969 ) (35.7 torre) = 34.6 torre

McMurray: Read Section 11.6 pages 413-419

McMurray-See worked Examples 11.8 p 416; 11.9 p417

Try Problems 11.13 and 11.14 p 417

End of Chapter Exercises: Colligative Properties

Exercises: non-volatile Solute: 11.82-11.83; Volatile Solute: 11.88-11.89

See Kotz Example 14.5 p 673-674

Work Kotz Exercise 14.5 p674

Similar Problems: Kotz 6th Chapter 14 p693 p 25-28