Question

A barometer tube is 80cm long (above the mercury reservoir).It reads 76cm in a particular day. A small amount of water is introduced in the tube and the reading drops to 75.4cm. Find the relative humidity in the sapce above the mercury cloumn if the saturation vopour pressure at the room temperature is 1.0cm.

Answer 1

Atmospheric pressure = 76 cm of Hg
When water is introduced the water
vapour exerts some pressure which
counter acts at the atmospheric pressure
The pressure drops to 75.4 cm
Pressure of vapour
= ( 76-75.4) cm `
= 0.6 cm
Relative Humidity
` =VP/SVP = 0.6cm/ 1cm = 60%` .