$a/$
$pthh:$
$4P +5O2 → 2P2O5$
$ nP=2,325/31=0,075mol$
$⇒nO2=4/5.nP=4/5.0,075=0,06mol$
$⇒mO2=0,06.32=1,92g$
$b/$
$pthh:$
$C+O2→CO2$
$nC=24/12=2mol$
$⇒nO2=nC=2mol$
$⇒mO2=2.32=64g$
$c/$
$nH2=1,121/22,4=0,05mol$
$pthh:$
$2H2+O2→2H2O$
$nO2=1/2.nH2=1/2.0,05=0,025mol$
$⇒mO2=0,025.32=0,8g$
$d/$
$nAl=4,05/27=0,15mol$
$pthh:$
$4Al + 3O2 → 2Al2O3$
$theo$ $pt :$
$nO2=3/4.nAl=3/4.0,15=0,1125mol$
$⇒mO2=0,1125.32=3,6g$