a, S là phi kim:
$S+ O_2 \buildrel{{t^o}}\over\to SO_2$
$S+ H_2 \buildrel{{t^o}}\over\to H_2S$
$S+ Zn \buildrel{{t^o}}\over\to ZnS$
b,
(1) $Cl_2+ H_2 \buildrel{{as}}\over\to 2HCl$
(2) $Cu+ Cl_2 \buildrel{{t^o}}\over\to CuCl_2$
(3) $CuO+ 2HCl \to CuCl_2+ H_2O$