30,8g(Fe2O3, Fe3O4, ZnO, CuO)+CO\(\rightarrow\)B(Fe, Zn, Cu)+CO2
CO2+Ca(OH)2\(\rightarrow\)CaCO3+H2O
\(n_{CO_2}=n_{CaCO_3}=\dfrac{40}{100}=0,4mol\)
CO+O(oxit)\(\rightarrow\)CO2
\(n_{O\left(oxit\right)}=n_{CO_2}=0,4mol\)\(\rightarrow\)\(m_{O\left(oxit\right)}=0,4.16=6,4g\)
\(\rightarrow\)mB=30,8-6,4=24,4 gam