Đáp án:
38.A
39.C
Giải thích các bước giải:
câu 38:
\(\begin{array}{l}
Zn + 2HCl \to ZnC{l_2} + {H_2}\\
2Al + 6HCl \to 2AlC{l_3} + 3{H_2}\\
\end{array}\)
\({n_{{H_2}}} = 0,15mol\)
\(\begin{array}{l}
{n_{Zn}} = {n_{{H_2}}} = 0,15mol\\
\to {m_{Zn}} = 0,15 \times 65 = 9,75g\\
{n_{Al}} = \dfrac{3}{2}{n_{{H_2}}} = 0,1mol\\
\to {m_{Al}} = 0,1 \times 27 = 2,7g
\end{array}\)
câu 39:
\(\begin{array}{l}
{P_2}{O_5} + 3{H_2}O \to 2{H_3}P{O_4}\\
{n_{{H_2}O}} = 5mol\\
{n_{{P_2}{O_5}}} = 0,2mol\\
\to {n_{{H_2}O}} > {n_{{P_2}{O_5}}}\\
\to {n_{{H_3}P{O_4}}} = 2{n_{{P_2}{O_5}}} = 0,4mol\\
\to {m_{{H_3}P{O_4}}} = 0,4 \times 98 = 39,2g
\end{array}\)
