\(Đặt:n_{KClO_3\left(LT\right)}=a\left(mol\right)\\ 2KClO_3\underrightarrow{^{to}}2KCl+3O_2\\ n_{KCl}=a\left(mol\right)\\ m_{rắn}=30,99\\ \Leftrightarrow\left(36,75-122,5a\right)+74,5a=30,99\\ \Leftrightarrow a=0,12\\ m_{KClO_3\left(LT\right)}=0,12.122,5=14,7\left(g\right)\\ H=\dfrac{14,7}{36,75}.100=40\%\)