\(CaCO_3\rightarrow\left(t^o\right)CaO+CO_2\\ n_{CaCO_3}=\dfrac{200}{100}=2\left(mol\right)\\ n_{CaO}=\dfrac{100,8}{56}=1,8\left(mol\right)\\ V\text{ì}:\dfrac{2}{1}>\dfrac{1,8}{1}\Rightarrow CaCO_3d\text{ư}\\ n_{CaCO_3\left(p.\text{ứ}\right)}=n_{CaO}=1,8\left(mol\right)\\ m_{CaCO_3\left(d\text{ư}\right)}=200-1,8.100=20\left(g\right)\)