posted by Jake .
The normal boiling point of a liquid is
A. the temperature at which all three phases are in equilibrium.
B. the only temperature at which there can be equilibrium between the liquid and gas states.
C. the temperature at which the vapor pressure equals 760 mmHg.
D. the temperature above which the substance cannot exist as a liquid regardless of the pressure.
E. the temperature at which the amounts of liquid and gas are equal
I think the answer you want is C; however, I must point out that if you boil a liquid when the pressure is less than 760 (say 750 torr), the liquid will boil when the vapor pressure of the liquid is 750 and not 760 torr. I think the word "normal" in the post makes the assumption that standard pressure of 760 torr prevails.