b)M Fe\(_2\)(SO\(_4\))\(_3\)=56.2+(32+16.4).3=400
1 mol Fe\(_2\)(SO\(_4\))\(_3\) có chứa 2 mol Fe, 12 mol O, 3 mol S
%mFe= mFe/400.100%= .100%=24%
%mS= mS/400.100%=24%
%mO= mO/400.100%=48%
#Fiona
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\(\%m_{Fe}=\dfrac{112.100\%}{400}=28\%\)
\(\%m_S=\dfrac{96.100\%}{400}=24\%\)
\(\Rightarrow\%m_O=100\%-28\%-24\%=48\%\)