Hướng dẫn:

${{n}_{{{H}_{2}}}}=\frac{{{V}_{{{H}_{2}}}}}{22,4}=\frac{5,6}{22,4}=0,25\left( mol \right)$

$A+2HCl\to muoiA+{{H}_{2}}$

        0,5   $\leftarrow $                0,25         (mol)

Theo phương trình ta có: ${{n}_{HCl}}=2.{{n}_{{{H}_{2}}}}=2.0,25=0,5\left( mol \right)$

$\Rightarrow {{m}_{HCl}}={{n}_{HCl}}.{{M}_{HCl}}=0,5.36,5=18,25\left( g \right)$

${{m}_{{{H}_{2}}}}={{n}_{{{H}_{2}}}}.{{M}_{{{H}_{2}}}}=0,25.2=0,5\left( g \right)$

Theo định luật bảo toàn khối lượng: ${{m}_{A}}+{{m}_{HCl}}={{m}_{muoiA}}+{{m}_{{{H}_{2}}}}$

$\Rightarrow {{m}_{A}}={{m}_{muoiA}}+{{m}_{{{H}_{2}}}}-{{m}_{HCl}}$

$\Rightarrow {{m}_{A}}=27,8+0,5-18,25=10,05\left( g \right)$

$\Rightarrow $ Chọn đáp án C