a) Fe2O3----> \(\dfrac{56.2}{56.2+16.3}.100\%=70\%\\ =>100\%-70\%=30\%\)
b) Fe3O4---->\(\dfrac{56.3}{56.3+16.4}.100\%=72,41\%\\ =>100\%-72,41\%=27,59\%\)
c)SO3---->\(\dfrac{32}{32+16.3}.100\%=40\%\\ =>100\%-40\%=60\%\)
d) CuSO4--->\(\dfrac{64}{64+32+16.4}.100\%=40\%\\ =>100\%-40\%=60\%\)
g) CH4-----> \(\dfrac{12}{12+1.4}.100\%=75\%\\ =>100\%-75\%=25\%\)