Chapter 3, Problem 3.7P

Interpretation Introduction

Interpretation:

The viscosity of halogen gases and normal paraffins versus their molecular weight at ${20}^{\circ }\text{C}$ and moderate pressure is to be plotted. The trends shown by the two plots are to be discussed.

Concept Introduction:

The value of viscosity in gases depends on the molecule’s average momentum. This momentum is directly dependent on the product of the molecular weight of the gas and its velocity which in turn is dependent on the square root of the ratio of temperature and molecular weight. The viscosity is also dependent on the mean-free path of the molecules. This mean-free path decreases with an increase in the molecule size. For non-interacting molecules of gases, the theory which is applicable is:

  $\mu =0.00267\frac{{\left(MT\right)}^{1/2}}{{\sigma }^2}$

Here, $\mu$ is the viscosity in cP, $M$ is the molecular weight, $T$ is the absolute temperature of the gas in K, and $\sigma$ is the diameter of the molecule in $\stackrel{\circ }{\text{A}}$ .