\(n_{Fe_3O_4}=\dfrac{2.32}{232}=0.01\left(mol\right)\)
\(3Fe+2O_2\underrightarrow{t^0}Fe_3O_4\)
\(0.03.....0.02......0.01\)
\(m_{Fe}=0.03\cdot56=1.68\left(g\right)\)
\(m_{O_2}=0.02\cdot32=0.64\left(g\right)\)
\(2KMnO_4\underrightarrow{t^0}K_2MnO_4+MnO_2+O_2\)
\(m_{KMnO_4}=0.02\cdot2\cdot158=6.32\left(g\right)\)