Just as a heads up, XChat hasn’t been maintained actively, almost since 2010. So you’d probably should think in using another client.
so xchat is removed from Ubuntu’s official repositories , but if you want install as you are a die hard fan of xchat , you can use Ubuntu-Play-store version of xchat which does not conflict with dependencies as it is a rebuild of xchat from source for ubuntu 16.04 by Keshav Bhatt for his Play store repositories .
to install just install Ubuntu play store client and look for xchat in list and click download and then click installer button to install xchat .
get it here :-
Download Latest .deb for : ( these links automatically points to latest build of play store you can get latest version from here )
NOTE: install with gdebi ,do not use dpkg -i here’s why