$n_{KClO_3}=73,5/122,5=0,6mol$
$a/2KClO_3\overset{t^o}\to 2KCl+3O_2$
b/Theo pt :
$n_{O_2}=3/2.n_{KClO_3}=3/2.0,6=0,9mol$
$⇒V_{O_2}=0,9.22,4=20,16l$
$c/3Fe+2O_2\overset{t^o}\to Fe_3O_4$
Theo pt :
$n_{Fe_3O_4}=1/2.n_{O_2}=1/2.0,9=0,45mol$
$⇒m_{Fe_3O_4}=0,45.232=104,4g$
$d/2Zn+O_2\overset{t^o}\to 2ZnO$
$n_{ZnO}=2.n_{O_2}=2.0,9=1,8mol$
$⇒m_{ZnO}=1,8.81=145,8g$
$f/4P+5O_2\overset{t^o}\to 2P_2O_5$
$n_{P_2O_5}=2/5.n_{O_2}=2/5.0,9=0,36mol$
$⇒m_{P_2O_5}=0,36.142=51,12g$