1/
$2H_2+O_2\overset{t^o}\to 2H_2O$
$PbO+H_2\overset{t^o}\to Pb+H_2O$
$Ag_2O+H_2\overset{t^o}\to Ag+H_2O$
$Fe_2O_3+3H_2\to 2Fe+3H_2O$
2/
$n_{Fe_2O_3}=1/160=0,00625mol$
$Fe_2O_3+3H_2\to 2Fe+3H_2O$
$\text{Theo pt :}$
$n_{H_2}=3.n_{Fe_2O_3}=3.0,00625=0,01875mol$
$⇒V_{H_2}=0,01875.22,4=0,42l$