1/
$2Al+6HCl\to 2AlCl_3+3H_2$
$\text{⇒Pư thế}$
$Fe_2O_3+3Cu\to 2Fe+3CuO$
$\text{⇒Pư thế}$
$4Na+O_2\overset{t^o}\to 2Na_2O$
$\text{⇒Pư hóa hợp}$
$CaCO_3\overset{t^o}\to CaO+CO_2$
$\text{⇒Pư phân hủy}$
2/
$n_P=12,4/31=0,4mol$
$a/4P+5O_2\overset{t^o}\to 2P_2O_5$
`b.Theo` `pt :`
$n_{P_2O_5}=1/2.n_P=1/2.0,4=0,2mol$
$⇒m_{P_2O_5}=0,2.142=28,4g$