Gọi x, y là số mol $KClO_3$, $KMnO_4$
$\Rightarrow 122,5x+158y=4,385$ (1)
$2KClO_3\buildrel{{t^o}}\over\to 2KCl+3O_2$
$2KMnO_4\buildrel{{t^o}}\over\to K_2MnO_4+MnO_2+O_2$
$\Rightarrow n_{O_2}=1,5x+0,5y (mol)$
Y gồm CO (a mol), $CO_2$ (b mol)
$n_Y=\dfrac{0,84}{22,4}=0,0375(mol)$
$\Rightarrow a+b=0,0375$ (*)
$\overline{M}_Y=16.2=32$
$\Rightarrow 28a+44b=32.0,0375$ (**)
(*)(**)$\Rightarrow a=0,028125; b=0,009375$
$C+O_2\buildrel{{t^o}}\over\to CO_2$
$2C+O_2\buildrel{{t^o}}\over\to 2CO$
$\Rightarrow n_{O_2}=0,5a+b=0,0234375$
$\Rightarrow 1,5x+0,5y=0,0234375$ (2)
(1)(2)$\Rightarrow x=0,0086; y=0,021$
$\%m_{KClO_3}=\dfrac{122,5.0,0086.100}{4,385}=24,025\%$
$\%m_{KMnO_4}=75,975\%$