Question
Positive deviation from ideal behaviour takes place because of
A.
Molecular interaction between atoms and $$\frac{{PV}}{{nRT}} > 1$$
B.
Molecular interaction between atoms and $$\frac{{PV}}{{nRT}} < 1$$
C.
Finite size of atoms and $$\frac{{PV}}{{nRT}} > 1$$
D.
Finite size of atoms and $$\frac{{PV}}{{nRT}} < 1$$
Answer :
Finite size of atoms and $$\frac{{PV}}{{nRT}} > 1$$
Solution :
For positive deviation : $$PV = nRT + nPb$$
$$ \Rightarrow \frac{{PV}}{{nRT}} = 1 + \frac{{Pb}}{{RT}}$$
Thus, the factor nPb is responsible for increasing the $$PV$$ value, above ideal value. $$b$$ is actually the effective volume of molecule. So, it is the finite size of molecules that leads to the origin of $$b$$ and hence positive deviation at high pressure.