Stoichiometry - Engineering

Q1:

Air at a temperature of 20°C and 750 mm Hg pressure has a relative humidity of 80%. What is its percentage humidity ? Vapour pressure of water at 20°C is 17.5 mm Hg.

A 80.38

B 80

C 79.62

D 78.51

ANS:C - 79.62

To find the percentage humidity of the air, we first need to calculate the vapor pressure of water in the air at 20°C and 80% relative humidity. Given:

  • Temperature 𝑇=20°𝐶T=20°C
  • Pressure of air 𝑃air=750 mm HgPair​=750mm Hg
  • Relative humidity 𝑅𝐻=80%RH=80%
  • Vapor pressure of water at 20°C 𝑃water=17.5 mm HgPwater​=17.5mm Hg
The vapor pressure of water in the air (𝑃water, airPwater, air​) can be calculated using the formula for relative humidity: