Câu hỏi 8

\(\left\{ \begin{gathered}
{\text{Mg}} \hfill \\
{\text{Al}} \hfill \\
\end{gathered} \right. + \left\{ \begin{gathered}
{\text{a}}\,{\text{mol}}\,{\text{AgN}}{{\text{O}}_{\text{3}}} \hfill \\
{\text{2a}}\,{\text{mol}}\,{\text{Cu(N}}{{\text{O}}_{\text{3}}}{{\text{)}}_{\text{2}}} \hfill \\
\end{gathered} \right. \to {\text{45}}{\text{,2g}}\,{\text{cr}}\,{\text{Y}}\xrightarrow{{ + {{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{{\text{4}}}}}}{\text{0}}{\text{,35}}\,{\text{mol}}\,{\text{S}}{{\text{O}}_{\text{2}}}\)

Giả sử chất rắn Y gồm Ag (a mol), Cu (2a mol)

\({{\text{m}}_{\text{Y}}} = {{\text{m}}_{{\text{Ag}}}} + {{\text{m}}_{{\text{Cu}}}} \Leftrightarrow {\text{108a}} + {\text{64}}{\text{.2a}} = {\text{45}}{\text{,2}} \Leftrightarrow {\text{a}} = {\text{0}}{\text{,192}}\,{\text{mol}}\)

\({{\text{n}}_{{\text{e}}\,{\text{nhuong}}}} = {{\text{n}}_{{\text{Ag}}}} + {\text{2}}{{\text{n}}_{{\text{Cu}}}} = {\text{0}}{\text{,192}} + {\text{2}}{\text{.2}}{\text{.0}}{\text{,192}} = {\text{0}}{\text{,96}} > {\text{2}}{{\text{n}}_{{\text{S}}{{\text{O}}_{\text{2}}}}} = {\text{2}}{\text{.0}}{\text{,35}} = {\text{0}}{\text{,7}}\)

Mg và Al phản ứng hết và Cu²⁺ dư.

Ta có hệ pt: 

\(\left\{ \begin{gathered}
{\text{108}}{{\text{n}}_{{\text{Ag}}}} + {\text{64}}{{\text{n}}_{{\text{Cu}}}} = {\text{45}}{\text{,2}} \hfill \\
{{\text{n}}_{{\text{Ag}}}} + {\text{2}}{{\text{n}}_{{\text{Cu}}}} = {\text{2}}{{\text{n}}_{{\text{S}}{{\text{O}}_{\text{2}}}}} = {\text{0}}{\text{,7}} \hfill \\
\end{gathered} \right. \Leftrightarrow \left\{ \begin{gathered}
{{\text{n}}_{{\text{Ag}}}} = {\text{0}}{\text{,3}} = {\text{a}} \hfill \\
{{\text{n}}_{{\text{Cu}}}} = {\text{0}}{\text{,2}} \hfill \\
\end{gathered} \right.\)

Đáp án B