Gọi \(\left\{{}\begin{matrix}n_{Fe}=a\left(mol\right)\\n_{Mg}=b\left(mol\right)\end{matrix}\right.\)
=> 56a + 24b = 8 (*)
\(n_{H_2}=\dfrac{4,48}{22,4}=0,2\left(mol\right)\)
PTHH:
\(Fe+2HCl\rightarrow FeCl_2+H_2\)
a--------------------------->a
\(Mg+2HCl\rightarrow MgCl_2+H_2\)
b--------------------------->b
=> a + b = 0,2 (**)
Từ (*), (**) => a = b = 0,1
=> \(\left\{{}\begin{matrix}\%m_{Fe}=\dfrac{0,1.56}{8}.100\%=70\%\\\%m_{Mg}=100\%-70\%=30\%\end{matrix}\right.\)
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Gọi \(n_K=a\left(mol\right)\Rightarrow n_{Ca}=3a\left(mol\right)\)
\(n_{H_2}=\dfrac{15,68}{22,4}=0,7\left(mol\right)\)
PTHH:
\(2K+2H_2O\rightarrow2KOH+H_2\)
a----------------------------->0,5a
\(Ca+2H_2O\rightarrow Ca\left(OH\right)_2+H_2\)
3a-------------------------->3a
=> 3a + 0,5a = 0,7
=> a = 0,2
=> \(\left\{{}\begin{matrix}\%m_K=\dfrac{0,2.39}{0,2.39+0,2.3.40}.100\%=24,53\%\\\%m_{Ca}=100\%-24,53\%=75,47\%\end{matrix}\right.\)
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Gọi \(\left\{{}\begin{matrix}n_{Ca}=x\left(mol\right)\\n_{Zn}=y\left(mol\right)\\n_{Al}=z\left(mol\right)\end{matrix}\right.\)
=> 40x + 65y + 27z = 30,4 (*)
\(n_{H_2\left(H_2O\right)}=\dfrac{6,72}{22,4}=0,3\left(mol\right);n_{H_2\left(H_2SO_4\right)}=\dfrac{11,2}{22,4}=0,5\left(mol\right)\)
PTHH:
\(Ca+2H_2O\rightarrow Ca\left(OH\right)_2+H_2\)
x------------------------------->x
\(Zn+H_2SO_4\rightarrow ZnSO_4+H_2\)
y----------------------------->y
\(2Al+3H_2SO_4\rightarrow Al_2\left(SO_4\right)_3+3H_2\)
z------------------------------------->1,5z
=> x = 0,3 (**)
y + 1,5z = 0,5 (***)
Từ (*), (**), (***) => a = 0,3; b = c = 0,2
=> \(\left\{{}\begin{matrix}m_{Ca}=0,3.40=12\left(g\right)\\m_{Zn}=0,2.65=13\left(g\right)\\m_{Al}=0,2.27=5,4\left(g\right)\end{matrix}\right.\)
