Pure water vapour is trapped in a vessel of volume 10 cm 3 . The relative humidity is 40%. The vapour is compressed slowly and isothermally. Find the volume of the vapour at which it will start condensing.

Question

Philoid · Accepted Answer

Given

Relative humidity= 40%

Initial volume of vapor V₁=10cm³=10.

Let saturation vapor pressure be P_o

So, initial pressure of vapours= P₁=0.4P_o

As mentioned in question, final stage comes when vapours start to condense.

When vapor starts to condense, relative humidity becomes 100% and vapor pressure attains the maximum pressure called saturation vapor pressure.

So final pressure of vapor P₂=P_o

Since the process is isothermal, temperature remains constant throughout. Applying Boyle’s law which states that PV=constant, if temperature is constant.

P₁V₁=P₂V₂

the volume of the vapour at which it will start condensing is 410^-6m³

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.

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.