Pure water vapour is trapped in a vessel of volume 10 cm3. The relative humidity is 40 %. The vapour is compressed slowly and isothermally. Find the volume of the vapour at which it will start condensing.
RH=VPSVP
The point where the vapour start condensing,
VP= SVP
We know P1V1=P2V2
RH×SVP×10=SVP×V2
⇒V2=10RH
= 10 × 0.4
= 4 cm