1/
$n_{KClO_2}=12,25/122,5=0,1mol$
$2KClO_3\overset{t^o}\to 2KCl+3O_2$
$\text{Theo pt :}$
$n_{O_2}=3/2.n_{KClO_3}=3/2.0,1=0,15mol$
$⇒V_{O_2}=0,15.22,4=3,36l$
2/
$n_{O_2}=2,8/22,4=0,125mol$
$2KMnO_4\overset{t^o}\to K_2MnO_4+MnO_2+O_2$
$\text{Theo pt :}$
$n_{KMnO_4}=2.n_{O_2}=2.0,125=0,25mol$
$⇒m_{KMnO_4}=0,25.158=39,5g$