Sounds just like most large classes I've ever taken through undergrad and respiratory therapy school. The only thing you mention that sounds like an issue worth bothering about is the loud snickering during Q&A/lecture, the rest of the stuff you just need to ignore.
What is gchat?
In response to some of the other comments here: it's great to have people you can be immature, be able to have a beer, play a game, etc with, but I'm not so sure I'd assume that everyone who sits there facebooking and snickering throughout class automatically falls under "cool people to hang out with", or the people who will be best with patients. Only time will tell~
No one here really knows exactly what your class is like, so ignore all the subjective and presumptuous, even nasty, comments here; you can see clearly that many of them aren't really answering your question anyway. Like someone else said, just ignore the stuff people do privately (ie on their laptops, etc), move seats away from any chatty/loud people, and then re-focus the energy you spent being annoyed by that stuff to studying or to something more productive.
Best of luck!