Question

(a) What is the difference between gas and vapour? 

(b) Analyse the vapour pressure vs temperature curve shown below:

Arrange the compounds shown in the graph in the decreasing order of their normal boiling points,

(c) The density of a gas was found to be 2.92 g L1 at 27 °C and 2.0 atm. Calculate the molar mass of the gas.

Answer 1

(a) A gas below its critical temperature can be liquified by applying pressure. Under these conditions, it is called vapour of the substance. 

(b) water > ethyl alcohol > carbon tetrachloride > diethyl ether

(c) M = \(\frac{dRT}{p}\) 

\(\frac{2.92\,gL^{-1}\times\,0.0821L\,atm\,K^{-1}\,mol^{-1}\times 300\,K}{2\,atm}\) 

= ^-136g mol