A2.00-l sample of was collected over water at a total pressure of 750. torr and 22 °c. when the was dried (water vapor removed), the gas had a volume of 1.95 l at 22 °c and 750. torr. calculate the vapor pressure of water at 22 °c.

Answer : The vapor pressure of water at is 1.01 atm.

Explanation :

Boyle's Law : It is defined as the pressure of the gas is inversely proportional to the volume of the gas at constant temperature and number of moles.

or,

where,

= initial pressure = ?

= final pressure = 750 torr = 0.987 atm    (1 atm = 760 torr)

= initial volume = 1.95 L

= final volume =  2.00 L

Now put all the given values in the above equation, we get:

Therefore, the vapor pressure of water at is 1.01 atm.