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The vapor pressure of liquid iodomethane, CH_3I, is 100 mm Hg at 266 K. A sample

ID: 1060571 • Letter: T

Question

The vapor pressure of liquid iodomethane, CH_3I, is 100 mm Hg at 266 K. A sample of CH_3I is placed 10 a closed, evacuated 520 mL container at a temperature of 266 K. It is found that all of the CH_3I is in the vapor phase and that the pressure is 74.0 mm Hg. If the volume of the container is reduced to 333 mL at constant temperature, which of the following statements are correct? Choose all that apply. Liquid iodomethane will be present. The pressure in the con tamer will be 116 mm Hg. Some of the vapor initially present will condense No condensation will occur. Only iodomethane vapor will be present.

Explanation / Answer

According to ideal gas equation,

PV = nRT,

The amount of Iodometahne is constant through out the process. So no.of moles of Iodomethane is constant. And Temperature is also constant. R is gas constant.

Then the equation becomes P1/P2 = V2/V1

P1= 74.0 mm

P2 = ??

V2 = 333 mL

V1= 520 mL

By substituting the given data

P2 = 74 * 520 /333 = 115.5 mm Hg

***The pressure in the container is 115.6 mm Hg, that means the pressure in the container is more than vapour pressure(100 mm Hg at 266 K). So there is no longer vapour in the container, the Iodomethane is condensed and in the form of liquid.