Question

If liquid water is introduced into an evacuated (zero pressure) flask, the pressure will begin to rise.

a) Eventually, the pressure will stop rising and reach a constant value. Why does it stop rising?

b) What do we call this pressure?

c) What will happen to this pressure if we increase the temperature of the flask? Why?

Answer 1

when liquid water is introduced into an evacuated space , since in vaccum the boiling point of water gets reduced, the water starts boiling at lower temperature. This continues for some time until the vapor above is in equilibrium with the liquid. This is the point at which the rate of evaporation becomes equal to rate of condensation and this pressure is called vapor pressure.

when temperature is increased, the tendency of liqud to go into the vapor phase increases and there will be more vaporization and the pressure builds up. higher the temperature, higher the vapor pressure.