Question

For real gases, van der Waals equation is written as $\left(p + \frac{a n^{2}}{V^{2}}\right)\left(\right.V-nb\left.\right)=nRT$

where a and b are van der Waals constants two sets of gases are

$\left(\right.I\left.\right)$ $O_{2},CO_{2},H_{2}$ and He

$\left(\right.II\left.\right)$ $CH_{4},O_{2}$ and $H_{2}$

The gases given in set-I in increasing order of b and gases given in set-II in decreasing order of a, are arranged below. Select the correct order from the following

• A. $\left(\right.I\left.\right)He < H_{2} < CO_{2} < O_{2},\left(\right.II\left.\right)CH_{4}>H_{2}>O_{2}$
• B. $\left(\right.I\left.\right)O_{2} < He < H_{2} < CO_{2},\left(\right.II\left.\right)H_{2}>O_{2}>CH_{4}$
• C. $\left(\right.I\left.\right)H_{2} < He < O_{2} < CO_{2},\left(\right.II\left.\right)CH_{4}>O_{2}>H_{2}$
• D. $\left(\right.I\left.\right)H_{2} < O_{2}>He>CO_{2},\left(\right.II\left.\right)O_{2}>CH_{4}>H_{2}$

Answer 1

Answer: (C)

Van der Waals gas constant 'a' represent intermolecular force of attraction of gaseous molecules and Van der Waals gas constant 'b' represent effective size of molecules . Therefore order should be

$\left(\right.I\left.\right)H_{2} < He < O_{2} < CO_{2},\left(\right.II\left.\right)CH_{4}>O_{2}>H_{2}$