\(n_{KClO3}=\dfrac{5,25}{122,5}=\dfrac{3}{70}\left(mol\right)\)
a) PTHH : \(2KClO_3\xrightarrow[]{t^o}2KCl+3O_2\)
\(\dfrac{3}{70}\) \(\dfrac{3}{70}\) \(\dfrac{9}{140}\)
b) \(V_{O2\left(dktc\right)}=\dfrac{9}{140}.22,4=1,44\left(l\right)\)
c) \(m_{KCl\left(lt\right)}=\dfrac{3}{70}.74,5=\dfrac{447}{140}\left(mol\right)\)
\(\Rightarrow H\%=\dfrac{m_{tt}}{m_{lt}}.100\%=\dfrac{2,235}{\dfrac{447}{140}}.100\%=70\%\)