CaS + 2HCl=CaCl2+H2S H2S =H2+S S+H2=H2S H2S + 2NaCl = Na2S+2HCl Na2S+Pb(NO3)2=PBS+2NaNO3 2PbS+3O2=2PbO + SO2 2SO2+O2=2SO3 SO3+CaO=CaSO4