Đáp án đúng: C
11,82 (g).
$\displaystyle \begin{array}{l}\frac{{{\text{n}}_{\text{O}{{\text{H}}^{\text{-}}}}}}{{{\text{n}}_{\text{C}{{\text{O}}_{\text{2}}}}}}\,\text{=}\,\frac{\text{0}\text{,4}\text{.0}\text{,2}\text{.2}}{\text{0}\text{,1}}\,\text{=}\,\text{1}\text{,6}\\\text{C}{{\text{O}}_{\text{2}}}\,\text{+}\,\text{Ba(OH}{{\text{)}}_{\text{2}}}\,\xrightarrow{{}}\,\text{BaC}{{\text{O}}_{\text{3}}}\downarrow \,\,\text{+}\,\,{{\text{H}}_{\text{2}}}\text{O}\\\text{2C}{{\text{O}}_{\text{2}}}\,\text{+}\,\text{Ba(OH}{{\text{)}}_{\text{2}}}\,\xrightarrow{{}}\,\text{Ba(HC}{{\text{O}}_{\text{3}}}{{\text{)}}_{\text{2}}}\\\Rightarrow \left\{ \begin{array}{l}{{\text{n}}_{\text{BaC}{{\text{O}}_{\text{3}}}}}\,\text{+}\,{{\text{n}}_{\text{Ba(HC}{{\text{O}}_{\text{3}}}{{\text{)}}_{\text{2}}}}}\,\text{=}\,{{\text{n}}_{\text{Ba(OH}{{\text{)}}_{\text{2}}}}}\,\text{=}\,\text{0}\text{,08}\\{{\text{n}}_{\text{BaC}{{\text{O}}_{\text{3}}}}}\,\text{+}\,\text{2}{{\text{n}}_{\text{Ba(HC}{{\text{O}}_{\text{3}}}{{\text{)}}_{\text{2}}}}}\,\text{=}\,{{\text{n}}_{\text{C}{{\text{O}}_{\text{2}}}}}\,\text{=}\,\text{0}\text{,1}\end{array} \right.\\\Rightarrow \,{{\text{n}}_{\text{BaC}{{\text{O}}_{\text{3}}}}}\,\text{=}\,\text{0}\text{,06}\,\Rightarrow \,{{\text{m}}_{\text{BaC}{{\text{O}}_{\text{3}}}}}\,\text{=11}\text{,82}\,\text{gam}\end{array}$
