Giải thích các bước giải:
a.
PTHH: $3Fe + 2O_2 \overset{t^{\circ}}{\rightarrow} Fe_3O_4$
$n_{Fe_3O_4}=$ $\dfrac{6,96}{232}=0,03(mol)$
Theo PTHH $\rightarrow n_{Fe}= \dfrac{0,03*3}{1}=0,09(mol)$
$\rightarrow m_{Fe}= 0,09*56=5,04(g)$
Theo PTHH $\rightarrow n_{O_2}= \dfrac{0,03*2}{1}=0,06(mol)$
$\rightarrow V_{O_2(đktc)}=0,06*22,4=1,344(l)$
b.
PTHH $2KMnO_4 \overset{t^{\circ}}{\rightarrow} K_2MnO_4 + MnO_2 + O_2$
Theo PTHH $\rightarrow n_{KMnO_4}=$ $\dfrac{0,06*2}{1}=0,12(mol)$
$\rightarrow m_{KMnO_4}=0,12*158=18,96(g)$