Đáp án đúng: A
0,64
Sự oxi hóa
$\displaystyle \begin{array}{l}\text{Fe }\!\!~\!\!\text{ }\to ~\text{F}{{\text{e}}^{\text{2+}}}\text{ }\!\!~\!\!\text{ + }\!\!~\!\!\text{ 2e}\\\text{0,1 }\!\!~\!\!\text{ }\!\!~\!\!\text{ }\!\!~\!\!\text{ }\!\!~\!\!\text{ }\!\!~\!\!\text{ }\xrightarrow{{}}\text{ }\!\!~\!\!\text{ }\!\!~\!\!\text{ 0,2}\end{array}$
(vì sau phản ứng có chất rắn nên Fe chuyển lên Fe2+).
Sự khử
$\displaystyle \begin{array}{l}\,\,\text{3e }\!\!~\!\!\text{ }\,\,\,\,\text{+ }\!\!~\!\!\text{ }\,\,\,\text{ }\!\!~\!\!\text{ 4}{{\text{H}}^{\text{+}}}\text{ }\!\!~\!\!\text{ }\,\,\,\,\text{+ }\!\!~\!\!\text{ N}{{\text{O}}_{\text{3}}}^{\text{-}}~\to \text{ }NO~+~2{{H}_{2}}O\\\text{0,18 }\!\!~\!\!\text{ }\,\leftarrow \text{0,24}\to \text{0,06}\end{array}$
$\displaystyle \begin{array}{l}\,\,\text{C}{{\text{u}}^{\text{2+}}}\text{ }\!\!~\!\!\text{ }\,\,\,\text{+ }\!\!~\!\!\text{ }\,\,\,\,\,\,\,\,\text{2e }\!\!~\!\!\text{ }\,\,\,\,\,\,\,\,\to ~\,\,\,\,\text{ }\!\!~\!\!\text{ Cu }\!\!~\!\!\text{ }~\\\text{0,01 }\!\!~\!\!\text{ }\!\!~\!\!\text{ }\leftarrow ~\text{(0,2-0,18)=0,02}\end{array}$
⇒ mrắn = mCu pư =0,64 gam
