\(PCl_5\) is well known but \(NCl_5\) is not because nitrogen does not have vacant d-orbitals in its valence shell.
So, nitrogen cannot expand its octet.
On the other hand phosphorus has vacant d-orbitals in its valence shell which enables it to expand its octet.
Therefore, the correct option is (B): nitrogen doesn’t have d-orbitals in its valence shell.
Which one of the following graphs accurately represents the plot of partial pressure of CS₂ vs its mole fraction in a mixture of acetone and CS₂ at constant temperature?

In the given figure, the blocks $A$, $B$ and $C$ weigh $4\,\text{kg}$, $6\,\text{kg}$ and $8\,\text{kg}$ respectively. The coefficient of sliding friction between any two surfaces is $0.5$. The force $\vec{F}$ required to slide the block $C$ with constant speed is ___ N.
(Given: $g = 10\,\text{m s}^{-2}$) 