What is funny about this joke?

I believe the joke actually goes like this:

two chemists walk into a bar. The bartender says "What'll ya have?' The first chemist says: "I'll have h2O". The second chemist says: "I'll have H2O, too" the second chemist died.

(if you get it now, don't read on, b/c I am going to explain the joke, which some people do not like)

the second chemist made it sound like he said he wanted H2O2, which was you already know, is hydrogen peroxide, a deadly gas.

the second chemist actually said: I'll have H2o too-which is hydrogen peroxide-but he only wanted H2O.

Because hydrogen peroxide chemical formula is H2O2 lmao. That's pretty funny.

Because hydrogen peroxide is h2o2. "I'll have h2o too."

AND THAT IS THE JOKE WHICH IS FUNNIER THAT WAY