a) \(Na2CO3+2HCl-->2NaCl+H2O+CO2\)
x-------------2x(mol)
\(CaCO3+2HCl-->CaCl2+H2O+CO2\)
y--------------2y(mol)
b) \(n_{HCl}=0,4.1,5=0,6\left(mol\right)\)
\(Theo\) bài ta có hpt
\(\left\{{}\begin{matrix}106x+100y=31,2\\2x+2y=0,6\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=0,2\\y=0,1\end{matrix}\right.\)
\(m_{Na2CO3}=0,2.106=21,2\left(g\right)\)
\(m_{CaCO3}=0,1.100=10\left(g\right)\)