1. Tardigrade
  2. Question
  3. Chemistry
  4. For real gases van der Waals equation is written as ( p + (an2/V2) ) (V - nb) = nRT Where 'a' and 'b' are van der Waals constants . Two sets of gases are: (I) O2, CO2, H2 and He (II) CH4, O2 and H2 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 :

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Q. For real gases van der Waals equation is written as
$\bigg( p + \frac{an^2}{V^2} \bigg) (V - nb) = nRT$
Where 'a' and 'b' are van der Waals constants .
Two sets of gases are :
(I)$ O_2, CO_2, H_2$ and $He$ (II) $CH_4, O_2$ 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 :

AIPMTAIPMT 2012States of Matter

Solution:

As per actual data's
sequence of Vander Wall constant (a)
$\begin{matrix}&H_{2}&<&He&<&O_{2}&<&CO_{2}\\ value&0.244&&0.34&&1.36&&3.54\end{matrix}$
and sequence of Vander Wall constant (b)
$\begin{matrix}&CH_{4}&>&O_{2}&>&H_{2}\\ value&0.042&&0.031&&0.026\end{matrix}$