\(n_{Cl_2}=0,03\left(mol\right)\)
\(PTHH:A+Cl_2\underrightarrow{t^o}ACl_2\)
\(\left(mol\right)\) \(0,03\) \(0,03\) \(0,03\)
\(M_A=\dfrac{0,72}{0,03}=24\)
\(\rightarrow A:Mg\left(Magie\right)\\ \rightarrow B:MgCl_2\)
\(b.\)Theo định luật BTKL: \(m_B=0,72+2,13=2,85\left(g\right)\)