Hòa tan hoàn toàn hỗn hợp X gồm...

B

- Hướng dẫn giải

Đáp án B

$$\begin{gathered} Lấy 1 mol hỗn hợp \\ \Rightarrow \left\{\begin{array}{l}Fe: x mol\\ Mg:\left(1-x\right) mol\end{array}\right. \end{gathered}$$

$$\begin{gathered} Fe+2HCl\to FeC{l}_2+H_2\uparrow \\ x 2x x x \end{gathered}$$

$$\begin{gathered} Mg + 2HCl \to MgC{l}_2 + H_2\uparrow \\ \left(1-x\right) 2\left(1-x\right) \left(1-x\right) \left(1-x\right) \end{gathered}$$

$$\begin{gathered} n_{H_2}=1 mol, n_{HCl}=2 mol \\ \Rightarrow m_{ddHCl}=\frac{2.36,5.100}{20}=365g \\ {m}_{ddY}=56x+24\left(1-x\right)+365-1.2=387+32x \end{gathered}$$

$$\begin{gathered} C{\%}_{FeC{l}_2}=\frac{127x}{387+32x}.100\%=15,76\% \\ \Rightarrow x=0,5 mol \\ \Rightarrow C{\%}_{MgC{l}_2}=\frac{95.0,5}{387+32.0,5}.100\%=11,79\% \end{gathered}$$