The total pressure in a flask containing air and ethanol at 257C is 845 mm Hg. If the pressure of the air in the flask is 762 mm Hg, the vapor pressure of ethanol is ? mm Hg.
The sum of the pressures is equal to the total pressure in the flask.
To find the vapor pressure of ethanol in the flask, we need to subtract the pressure of the air from the total pressure in the flask.
Vapor pressure of ethanol = Total pressure - Pressure of air
Vapor pressure of ethanol = 845 mm Hg - 762 mm Hg
Vapor pressure of ethanol = 83 mm Hg
Therefore, the vapor pressure of ethanol in the flask is 83 mm Hg.