a, Các PTHH:
\(2KMnO_4\underrightarrow{^{to}}K_2MnO_4+MnO_2+O_2\)
\(4Al+3O_2\rightarrow2Al_2O_3\)
b,Ta có:
\(n_{Al}=\frac{5,4}{27}=0,2\left(mol\right)\Rightarrow\left\{{}\begin{matrix}n_{O2}=0,15\left(mol\right)\\n_{KMnO4}=0,3\left(mol\right)\end{matrix}\right.\)
\(\Rightarrow m_{KMnO4}=0,3.158=47,4\left(g\right)\)