# Oentane is a liquid with a vapor pressure of 512 Torr at 25C

1. Apr 13, 2005

### physicsss

Oentane is a liquid with a vapor pressure of 512 Torr at 25C; at the same temperature, the vapor pressure of hexane is only 151 Torr. what composition must the liquid phase have if the gas hase composition is to have equal amounts of pentane and hexane?

Do I use p = i M R T to solve for the M, molar masses? How do I need to get started

2. Apr 13, 2005

### GCT

No, you'll need to use the Rault's law

$$P=P_{pure~hexane}C_{hexane}+P_{pure~oentane}C_{oentane}$$

where C=molar composition of respective compound