CT :A(OH)2
\(m_{H_2O}=11.6-8=3.6\left(g\right)\)
\(n_{H_2O}=n_{AO}=\dfrac{3.6}{18}=0.2\left(mol\right)\)
\(A\left(OH\right)_2\underrightarrow{^{^{t^0}}}AO+H_2O\)
\(M_{AO}=\dfrac{8}{0.2}=40\left(\dfrac{g}{mol}\right)\)
\(\Rightarrow A=40-16=24\left(\dfrac{g}{mol}\right)\)
\(Mg\left(OH\right)_2\)