\(n_{KMnO_4\left(lt\right)}=\dfrac{31.6}{158}\cdot80\%=0.16\left(mol\right)\)
\(2KMnO_4\underrightarrow{^{^{t^0}}}K_2MnO_4+MnO_2+O_2\)
\(0.16.............................................0.08\)
\(V_{O_2}=0.08\cdot22.4=1.792\left(l\right)\)
n KMnO4 = 31,6/158 =0,2(mol)
$2KMnO_4 \xrightarrow{t^o} K_2MnO_4 + MnO_2 + O_2$
n O2(lt) = 1/2 n KMnO4 = 0,1(mol)
n O2(tt) = 0,1.80% = 0,08(mol)
V O2 = 0,08.22,4 = 1,792 lít