Chapter 6, Problem 6.12P

Interpretation Introduction

Interpretation:

The mole fraction of water in the air, the molal humidity, absolute humidity, and the percentage humidity in the air are to be calculated.

Concept introduction:

Mole fraction of water vapor in the air is defined as the number of moles of water vapor divided by the total number of moles of all species in the air. Mole fraction of a component of air may be calculated from the partial pressure of that component and the total pressure of all the components. The partial pressure is calculated as:

Partial pressure = Mole fraction × Total pressure of all the components

Molal humidity is expressed as:

$\text{Molal humidity = }\frac{\text{partial pressure of vapor in air }}{\text{total pressure - partial pressure of vapor}}\times 100$

Absolute humidity is a measure of water vapor in the air. It is expressed as:

$\text{Absolute humidity = }\frac{\text{Relative humidity}\times \text{partial pressure of vapor}}{\text{total air pressure}}$