Đáp án đúng: A
70 ml.
$\displaystyle \begin{array}{l}\text{HCO}_{\text{3}}^{\text{-}}\,\text{+}\,\text{O}{{\text{H}}^{\text{-}}}\,\xrightarrow{{}}\,\,\,\text{CO}_{\text{3}}^{\text{2-}}\,\text{+}\,{{\text{H}}_{\text{2}}}\text{O}\\\,\text{0,07}\,\,\,\,\,\,\,\text{0,07}\,\,\xleftarrow{{}}\,\,\,\text{0,07}\\\,\,\text{B}{{\text{a}}^{\text{2+}}}\,\text{+}\,\,\,\text{CO}_{\text{3}}^{\text{2-}}\,\xrightarrow{{}}\,\text{BaC}{{\text{O}}_{\text{3}}}\text{ }\!\!\bar{\ }\!\!\text{ }\\\text{0,07}\,\to \,\,\,\text{0,07}\\\Rightarrow \,{{\text{n}}_{\text{O}{{\text{H}}^{\text{-}}}}}\,\text{=}\,\text{0,07}\,\Rightarrow \,{{\text{V}}_{\text{NaOH}}}\,\text{=}\,\text{0,07}\,\text{lit}\end{array}$
