Đáp án đúng: A
43,11 gam.
$\displaystyle \begin{array}{l}\,\,\text{Fe + }\,\text{4}{{\text{H}}^{\text{+}}}\,\,\text{ + }\,\,\text{N}{{\text{O}}_{\text{3}}}^{\text{-}}\xrightarrow{{}}\text{F}{{\text{e}}^{\text{3+}}}\text{ + NO + 2}{{\text{H}}_{\text{2}}}\text{O}\\\text{0,06 }\,\,\,\text{0,24 }\,\,\,\,\,\,\,\,\,\,\,\,\text{0,06}\,\,\,\,\,\,\,\,\,\,\,\,\text{0,06}\\\text{Fe }\,\,\text{+}\,\,\text{ 2F}{{\text{e}}^{\text{3+}}}\xrightarrow{{}}\text{3F}{{\text{e}}^{\text{2+}}}\\\text{0,03}\,\,\,\,\,\,\text{0,06}\\\text{Fe + }\,\,\,\text{2}{{\text{H}}^{\text{+}}}\xrightarrow{{}}\text{F}{{\text{e}}^{\text{2+}}}\text{ + }{{\text{H}}_{\text{2}}}\\\text{0,04}\,\,\,\,\text{0,08}\\\text{F}{{\text{e}}^{\text{2+}}}\text{ + 2O}{{\text{H}}^{\text{-}}}\xrightarrow{{}}\text{Fe}{{\left( \text{OH} \right)}_{\text{2}}}\\\text{B}{{\text{a}}^{\text{2+}}}\text{ + S}{{\text{O}}_{\text{4}}}^{\text{2-}}\xrightarrow{{}}\text{BaS}{{\text{O}}_{\text{4}}}\end{array}$
Vậy kết tủa gồm Fe(OH)2, BaSO4 và Fe dư ⇒ x = 0,13.90 + 0,13.233 + 0,02.56 = 43,11.
