H2S+O2=S+H2O
AL+CL2=ALCL3
Cu+N2=Ca3N2
KBr+CL2=Br2+KCl
2H2S+O2=2S+2H2O 2AL+3CL2=2ALCL3 3Ca+N2=Ca3N2 2KBr+CL2=Br2+2KCl