\(a,\text{Đ}\text{ặt}:Fe^a\left(OH\right)^I_3\left(a:nguy\text{ê}n,d\text{ươ}ng\right)\\ QTHT:a.1=I.3\\ \Rightarrow a=\dfrac{I.3}{1}=III\\ \Rightarrow Fe\left(III\right)\)
\(b,\text{Đ}\text{ặt}:Cu^bCl^I_2\left(b:nguy\text{ê}n,d\text{ươ}ng\right)\\ QTHT:b.1=I.2\\ \Rightarrow b=\dfrac{I.2}{1}=II\\ \Rightarrow Cu\left(II\right)\)