The total pressure in a flask containing air and ethanol at 257C is 882 mm Hg. If the pressure of the air in the flask is 762 mm Hg, the vapor pressure of ethanol is _____ mm Hg.

Just subtract the PARTIAL pressure of air from the total pressure. The problem should have stated that 762 mm Hg was the partial pressure of air.

To find the vapor pressure of ethanol, we need to first calculate the partial pressure of ethanol in the flask.

Partial pressure is the pressure exerted by one component of a mixture of gases, assuming it alone occupies the total volume.

To calculate the partial pressure of ethanol, we need to subtract the pressure of air from the total pressure:

Partial pressure of ethanol = Total pressure - Pressure of air

Partial pressure of ethanol = 882 mm Hg - 762 mm Hg

Partial pressure of ethanol = 120 mm Hg

Therefore, the vapor pressure of ethanol in the flask is 120 mm Hg.