PTHH :
\(2KClO_3\overrightarrow{t^o}2KCl+3O_2\uparrow\)
\(n_{KClO_3}=\dfrac{12,25}{122,5}=0,1\left(mol\right)\)
Theo PTHH :
\(n_{O_2}=\dfrac{3}{2}n_{KClO_3}=0,15\left(mol\right)\)
\(V_{O_2}=0,15.22,4=3,36\left(l\right)\)
\(V_{O_{2thucte}}=3,36.80\%=2,688\left(l\right)\)