nO2=10,08/22,4=0,45(mol)
2KMnO4--t*->K2MnO4+MnO2+O2
0,9____________0,45_____0,45__0,45
mKMnO4=0,9.158=142,2(g)
=>m tạp chất=142,2.10/90=15,8(g)
mK2MnO4=0,45.197=88,65(g)
mMnO2=0,45.87=39,15(g)
=>mX=39,15+88,65+15,8=143,6(g)
=>%m tạp chất=15,8/143,6.100%=11%
%mK2MnO4=88,65/143,6.100%=61,7%
=>%mMnO2=100%-61,7%-11%=27,3%