a)\(n_{Mg}=\dfrac{35,6}{24}=1,483\left(mol\right)\)

  \(V_{O2\left(đktc\right)}=\dfrac{21,504}{22,4}=0,96\left(mol\right)\)

pt:    2Mg + O₂  →  2MgO (1)

mol:   2         1             2

mol:1,483    0,96

Tỉ lệ: \(\dfrac{1,483}{2}=0,7415< \dfrac{0,96}{1}=0,96\)

Mg tác dụng hết. O₂ dư

theo PTHH có

\(n_{O2p\intư}=\dfrac{1,843x1}{2}=0,7415\left(mol\right)\)

n_O2 dư=1,843-0,7415=1,1015 (mol)

m_O2dư= 1,1015 x 32 = 35,48 (g)

b)theo PTHH có

 \(n_{MgO}=\dfrac{1,843x2}{2}=1,843\left(mol\right)\)

n_MgO = 1,843 X 40 = 73,72 (g)

c)

n_{Mg PT(1)}=n_MgPT(2)=1,843 (mol)

pt:    Mg + H₂SO₄ ➝ MgSO₄ + H₂   (2)

mol:  1           1              1           1

mol:   1,843

Theo PTHH có

\(n_{H2}=\dfrac{1,843x1}{1}=1,843\) (mol)

m_H2=1,843 x 2 = 3,686 (g)

giúp minh với các bạn 

a, Cu không tác dụng với dd HCl.

PT: \(Zn+2HCl\rightarrow ZnCl_2+H_2\)

b, Ta có: \(n_{H_2}=\dfrac{4,48}{22,4}=0,2\left(mol\right)\)

Theo PT: \(n_{Zn}=n_{H_2}=0,2\left(mol\right)\)

\(\Rightarrow m_{Zn}=0,2.65=13\left(g\right)\)

\(\Rightarrow m_{Cu}=19,4-13=6,4\left(g\right)\)

c, Ta có: \(\left\{{}\begin{matrix}\%m_{Zn}=\dfrac{13}{19,4}.100\%\approx67,01\%\\\%m_{Cu}\approx32,99\%\end{matrix}\right.\)

Bạn tham khảo nhé!

PTHH: \(2Mg+O_2\underrightarrow{t^o}2MgO\)  (1)

            \(4Al+3O_2\underrightarrow{t^o}2Al_2O_3\)  (2)

Ta có: \(\left\{{}\begin{matrix}\Sigma n_{O_2}=\dfrac{33,6}{22,4}=1,5\left(mol\right)\\n_{Al}=\dfrac{2,7}{27}=0,1\left(mol\right)\Rightarrow n_{O_2\left(2\right)}=0,075\left(mol\right)\end{matrix}\right.\)

\(\Rightarrow n_{O_2\left(1\right)}=1,425\left(mol\right)\) \(\Rightarrow n_{Mg}=2,85\left(mol\right)\)

\(\Rightarrow\%m_{Mg}=\dfrac{2,85\cdot24}{2,85\cdot24+2,7}\cdot100\%\approx96,2\%\)

\(\Rightarrow\%m_{Al}=3,8\%\) 

\(n_{O_2} =\dfrac{33,6}{22,4} = 1,5(mol)\\ n_{Al} = \dfrac{2,7}{27} = 0,1(mol)\\ 2Mg + O_2 \xrightarrow{t^o} 2MgO\\ 4Al + 3O_2 \xrightarrow{t^o} 2Al_2O_3\\ n_{O_2} = \dfrac{1}{2}n_{Mg} + \dfrac{3}{4}n_{Al}\\ \Rightarrow n_{Mg} = 2,85(mol)\)

Vậy :

\(\%m_{Mg} = \dfrac{2,85.24}{2,85.24 + 2,7}.100\% = 96,2\%\\ \%m_{Al} = 100\% - 96,2\% = 3,8\%\)

Bài 1:

a+b) PTHH: \(Fe+H_2SO_4\rightarrow FeSO_4+H_2\uparrow\)

Ta có: \(n_{H_2}=\dfrac{4,48}{22,4}=0,2\left(mol\right)=n_{Fe}\)

\(\Rightarrow m_{Fe}=0,2\cdot56=11,2\left(g\right)\) \(\Rightarrow m_{Cu}=6,4\left(g\right)\)

\(\Rightarrow\left\{{}\begin{matrix}\%m_{Fe}=\dfrac{11,2}{17,6}\cdot100\%\approx63,64\%\\\%m_{Cu}=36,36\%\end{matrix}\right.\)

c) Ta có: \(n_{Cu}=\dfrac{6,4}{64}=0,1\left(mol\right)\)

Bảo toàn nguyên tố: \(n_{Fe_2\left(SO_4\right)_3}=\dfrac{1}{2}n_{Fe}=0,1\left(mol\right)=n_{CuSO_4}\)

\(\Rightarrow m_{muối}=0,1\cdot400+0,1\cdot160=56\left(g\right)\)

Bài 2:

Quy đổi hh gồm Fe (a mol) và O (b mol)

\(\Rightarrow56a+16b=27,6\)  (1)

Ta có: \(n_{SO_2}=\dfrac{5,04}{22,4}=0,225\left(mol\right)\)

Bảo toàn electron: \(3n_{Fe}=2n_O+2n_{SO_2}\) \(\Rightarrow3a-2b=0,45\)  (2)

Từ (1) và (2) \(\Rightarrow\left\{{}\begin{matrix}a=0,39\\b=0,36\end{matrix}\right.\)

Bảo toàn nguyên tố: \(n_{Fe_2\left(SO_4\right)_3}=\dfrac{1}{2}n_{Fe}=0,195\left(mol\right)\) \(\Rightarrow m_{Fe_2\left(SO_4\right)_3}=0,195\cdot400=78\left(g\right)\)

\(n_{Mg}=\dfrac{13}{24}=0,54mol\)

\(Mg+2HCl\rightarrow MgCl_2+H_2\)

0,54                     0,54               ( mol )

\(m_{MgCl_2}=0,54.95=51,3g\)

\(CuO+H_2\rightarrow\left(t^o\right)Cu+H_2O\)

            0,54          0,54               ( mol )

\(m_{Cu}=0,54.64=34,56g\)