Hướng dẫn:

${{n}_{{{H}_{2}}}}=\frac{{{V}_{{{H}_{2}}}}}{22,4}=\frac{3,36}{22,4}=0,15\left( mol \right)$ 

$R+{{H}_{2}}S{{O}_{4}}\to RS{{O}_{4}}+{{H}_{2}}$ 

                       0,15$\leftarrow $0,15      (mol)

Theo phương trình ta có:

${{n}_{RS{{O}_{4}}}}={{n}_{{{H}_{2}}}}=0,15\left( mol \right)$ 

${{m}_{RS{{O}_{4}}}}={{n}_{RS{{O}_{4}}}}.{{M}_{RS{{O}_{4}}}}\Rightarrow {{M}_{RS{{O}_{4}}}}=\frac{{{m}_{RS{{O}_{4}}}}}{{{n}_{RS{{O}_{4}}}}}$ 

$\Rightarrow {{M}_{R}}+{{M}_{S}}+4.{{M}_{O}}=\frac{22,8}{0,15}$ 

$\Rightarrow {{M}_{R}}=152-32-4.16=56$ 

R là sắt(Fe)

Chọn đáp án A