PTHH: \(CaO+2HCl\rightarrow CaCl_2+H_2O\)  (1)

           \(CaCO_3+2HCl\rightarrow CaCl_2+H_2O+CO_2\uparrow\)  (2)

a) Ta có: \(n_{CO_2}=\dfrac{4,48}{22,4}=0,2\left(mol\right)=n_{CaCO_3}\)

\(\Rightarrow m_{CaCO_3}=0,2\cdot100=20\left(g\right)\) \(\Rightarrow\%m_{CaCO_3}=\dfrac{20}{25,6}\cdot100\%=78,125\%\)

\(\Rightarrow\%m_{CaO}=21,875\%\)

b) Theo 2 PTHH: \(\left\{{}\begin{matrix}n_{HCl\left(2\right)}=2n_{CaCO_3}=0,4mol\\n_{HCl\left(1\right)}=2n_{CaO}=2\cdot\dfrac{25,6-20}{56}=0,2mol\end{matrix}\right.\)

\(\Rightarrow\Sigma n_{HCl}=0,6mol\) \(\Rightarrow C\%_{HCl}=\dfrac{0,6\cdot36,5}{210\cdot1,05}\cdot100\%\approx9,93\%\)