question_answer 62)

  For real gases the relation between P, V and T is given by van der Waals' equation : \[\left( p+\frac{a{{n}^{2}}}{{{V}^{2}}} \right)(V-nb)=nRT\] where 'a' and 'b? are van der Waals' constants, 'nb? is approximately equal to the total volume of the molecules of a gas. 'a' is the measure of magnitude of intermolecular attraction. (i) Arrange the following gases in the increasing order of ?b?. Give reason. \[{{O}_{2}},C{{O}_{2}},{{H}_{2}},He\] (ii) Arrange the following gases in the decreasing order of magnitude of ?a?. Give reason. \[C{{H}_{4}},{{O}_{2}},{{H}_{2}}\]                

Answer:

  (i) Bigger is the size of volume, greater is the value of van der Waals' constant 'b? \[\xrightarrow[Increasing\text{ }value\text{ }of\text{ }b]{{{H}_{2}}<He<{{O}_{2}}<C{{O}_{2}}}\] (ii) Greater is the intermolecular force, more is the value of van der Waals' constant 'a?. \[\xrightarrow[Decreasing\text{ }value\text{ }of\text{ }a']{C{{H}_{4}}>{{O}_{2}}>{{H}_{2}}}\]