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# Groupwork 11 Ideal and nonideal systems

Name: ______________________________

Section: _____________________________

Student ID#:__________________________

Work in groups on these problems. You should try to answer the questions without referring to your textbook. If you get stuck, try asking another group for help.

At 90 ˚C, the vapor pressure of toluene is 400 torr while that of o-xylene is 150 torr.

• What is the composition of a liquid mixture that will boil at 90 ˚C when the external pressure is 0.5 atmosphere?
• What is the composition of the vapor?
• What assumptions have you made?

FYI:1 atm =760 torr

Consider a mixture of 2,2,4-trimethyl pentane (iso-octane) and ethanol at 25 ˚C. At 0.2748 mole fraction of iso-octane, the partial vapor pressure of iso-octane is 48.31 torr and the vapor pressure of pure iso-octane is 59.03 torr. The partial vapor pressure of ethanol in the solution is 46.91 torr and the vapor pressure of pure ethanol is 49.31 torr.

• Is the mixture ideal or nonideal? If it is nonideal, does it deviate positively or negatively from ideality? Explain your answer.
• Could you ever have a solution where one component deviated positively from ideality and the other had a negative deviation?