Đặt \(\left\{{}\begin{matrix}n_{CaCO_3}=a\left(mol\right)\\n_{Na_2CO_3}=b\left(mol\right)\end{matrix}\right.\)
\(\left[C\right]:a+b=\dfrac{6,72}{22,4}=0,3\)
\(m=31,2\left(g\right)\Leftrightarrow100a+106b=31,2\)
\(\Leftrightarrow\left\{{}\begin{matrix}a=0,1\left(mol\right)\\b=0,2\left(mol\right)\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}m_{CaCO_3}=0,1.100=10\left(g\right)\\m_{Na_2CO_3}=106.0,2=21,2\left(g\right)\end{matrix}\right.\)