(N/A) $(i)$ Nitration of phenol with dilute $HNO_3$ yields a mixture of $o$-nitrophenol and $p$-nitrophenol.
$(ii)$ The components of this nitrophenol mixture are separated by the steam distillation method.
$(iii)$ Upon steam distillation of the mixture of $o$- and $p$-nitrophenol,$o$-nitrophenol distills over with steam and is separated,while $p$-nitrophenol remains in the flask.
$(iv)$ $o$-nitrophenol is volatile with steam due to the presence of intramolecular hydrogen bonding,allowing it to be separated.
$p$-nitrophenol is less volatile in steam distillation and remains in the flask because it exhibits intermolecular $H$-bonding,as shown below.