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Vapor Pressure and Temperature

ACTSCI-Y0BTDA

A student is conducting an experiment to determine what factors affect the vapor pressure of methanol. The student is measuring the vapor pressure of methanol using a mercury manometer, as pictured below.

The experimental apparatus has an evacuated 1.0 liter bulb, into which the student injects a measured amount of methanol. The methanol then vaporizes to a gas until the vapor pressure equilibrates with the liquid, by saturating the bulb volume with methanol vapor.

The temperature of the methanol is controlled by placing it in a water bath. The student measures the vapor pressure by determining the height of the mercury column after the methanol is injected.

Experiment 1 Results
The student first tried varying the volume of methanol injected into the bulb.

Experiment 2 Results
Next, the student tried varying the temperature of a fixed volume of methanol. The student made sure there was always methanol liquid in the glass bulb when the measurement of vapor pressure was taken.

Experiment 3 Results
Finally, the student tried measuring the vapor pressure of different substances, both with and without alcohol (-OH) groups, at 20° C.

Based on Experiment 2, methanol has a vapor pressure of 190 mmHg when the temperature was closest to

A

$0°C$

B

$8°C$

C

$20°C$

D

$55°C$