a) sắt + axit clohiđric → sắt II clorua + khí hiđrô
b) Theo định luật bảo toàn khối lượng:
\(m_{Fe}+m_{HCl}=m_{FeCl_2}+m_{H_2}\)
\(\Leftrightarrow5,6+7,3=m_{FeCl_2}+m_{H_2}\)
\(\Leftrightarrow m_{FeCl_2}+m_{H_2}=12,9\left(g\right)\)
Ta có: \(\left\{{}\begin{matrix}\dfrac{m_{FeCl_2}}{m_{H_2}}=\dfrac{127}{2}\\m_{FeCl_2}+m_{H_2}=12,9\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}m_{FeCl_2}=12,7\left(g\right)\\m_{H_2}=0,2\left(g\right)\end{matrix}\right.\)