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The vapor pressure of liquid propanol, C3H7OH, is 40.0 mm Hg at 309 K. A sample

ID: 991530 • Letter: T

Question

The vapor pressure of liquid propanol, C3H7OH, is 40.0 mm Hg at 309 K. A sample of C3H7OH is placed in a closed, evacuated container of constant volume at a temperature of 494 K. It is found that all of the C3H7OH is in the vapor phase and that the pressure is 60.0 mm Hg. If the temperature in the container is reduced to 309 K, which of the following statements are correct?

Choose all that apply.

The pressure in the container will be 40.0 mm Hg.

Some of the vapor initially present will condense.

Only propanol vapor will be present.

Liquid propanol will be present.

No condensation will occur.

Explanation / Answer

At constant volume the temperature and pressure are related to each other as follows:

P1/T1= P2/T2

Here P1 = 60.0 mmHg; T1=494K

P2= ? and T2= 309 K

P2= P1/T1*T2

P2 =60/494*309

P2 = 37.53 mmHg

Hence the correct answer is Some of the vapor initially present will condense.