(bleach + ammonia = chlorine gas + other stuff) Clorine gas = horrible death
More specifically, Chlorine Gas in your lungs makes Hydrochloric Acid inside of your lungs. Your lungs are melted by that acid while you drown from it. Truly, a terrible way to die. Homura would still be fine though, due to being a lich, as her Phylactery wouldn't be damaged. It would still be ungodly painful, though.
to a wonderful world.Don't mix them; it's dangerous!We're all on our wayEverybody here will get killed!Yes, this is a holy ceremony.You'll come to understand how wonderful a thing that is very soon.It's a little too early to make my appearance... I'd better observe a little longer...If I play this right, I can make my gallant entrance just in the nick of time...I shall protect Kaname Madoka!HaaHaaHaaHomura-chan, how wonderful!!Hitomi-chan, why...?Don't! It's dangerous!shatterPlease do not do this at home, kids.