Question

1. If the absolute humidity is 15.2mmHg in a lab at 20C and the saturated vapor pressure of water at 20C is 17.3mmHg, what is the relative humidity?

2. If the density of the above gas is1.964 g/liter at STP, what is the formula and molecular weight of the gas if it contains just C and O?

Answer 1

1. Relative humidity is given by

, where w = absolute humidity or actual water vapour concⁿ

                                                   w_e = saturated or equilibrium vapour pressure

2. Given density of the gas = 1.964 g/litre

The gas could be CO or CO₂; the relation to fing their density at STP is given as

Density at STP = molar mass X (1 mol/22.4 L)

For CO, density = 28 g/mol X (1 mol/22.4L) = 28g/22.4 L = 1.25 g/L

For CO₂, density = 44g/mol X (1mol/22.4L) = 1.9643 g/L

Thus, the gas is CO₂, carbon dioxide.