Question

The density of a gas is found to be 1.56 g/L at 745 mm pressure and ${65}^0$ C.What is the moleculer mass of the gas?

• A. 44.2 u
• B. 4.42 u
• C. 2.24 u
• D. 22.4 u

Answer 1

The correct option is A 44.2 u

We have

$\begin{array}{c}T={65}^{\circ }C=338K\\ P=745mofHg=\frac{745}{760}atm\end{array}$

Now by using formula

$\begin{array}{c}PV=nRT\\ PV=\frac{W}{M}RT\\ \Rightarrow PM=\left(\frac{W}{V}\right)RT\\ \Rightarrow PM=dRT\\ \therefore M=\frac{dRT}{P}\\ \Rightarrow M=\frac{1.56\times .0.821\times 338}{\frac{745}{760}}\\ \Rightarrow M=\frac{1.56\times 0.0821\times 338\times 152}{149}=44.2u\end{array}$