PTHH: \(Mg+2HCl\rightarrow MgCl_2+H_2\uparrow\)

             \(MgO+2HCl\rightarrow MgCl_2+H_2O\)

Ta có: \(n_{H_2}=\dfrac{2,24}{22,4}=0,1\left(mol\right)=n_{Mg}\)

\(\Rightarrow m_{Mg}=0,1\cdot24=2,4\left(g\right)\) \(\Rightarrow m_{MgO}=2\left(g\right)\)

mg+2hcl-> mgcl2+ h2

mgo+2hcl->mgcl2+ h2o

đặt nmg=a, nmgo=b

theo bài ra và theo pthh ta có hệ:

24a+40b=4,4

a=2,24/22,4

=> a=0,1, b=0,05

-> %m Mg=0,1*24/4,4*100=54,54%

%m MgO=100-54,54=45,45%

Cu + 2 H2SO4(đ) -to-> CuSO4 + SO2 + 2 H2O

x____2x_______________x______x(mol)

Mg + 2 H2SO4(đ) -to-> MgSO4 + SO2 + 2 H2O

y____2y__________y________y(mol)

Đặt: nCu=x(mol); nMg=y(mol) (x,y>0)

Ta có hpt:

\(\left\{{}\begin{matrix}64x+24y=11,2\\22,4x+22,4y=6,72\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=0,1\\y=0,2\end{matrix}\right.\)

mCu=0,1.64=6,4(g) ; mMg=0,2.24=4,8(g)

nH2SO4(p.ứ)=2x+2y=0,6(mol)

=>mH2SO4=0,6.98=58,8(g)

\(a,n_{H_2}=\dfrac{6,72}{22,4}=0,3(mol)\\ 2Al+6HCl\to 2AlCl_3+3H_2\\ \Rightarrow n_{Al}=0,2(mol)\\ \Rightarrow m_{Al}=0,2.27=5,4(g)\\ b,m_{hh}=5,4+12,8=18,2(g)\\ c,n_{HCl}=0,6(mol)\\ \Rightarrow C_{M_{HCl}}=\dfrac{0,6}{0,3}=2M\)

a) \(n_{H_2}=\dfrac{6,72}{22,4}=0,3\left(mol\right)\)

PTHH: 2Al + 6HCl --> 2AlCl₃ + 3H₂

_____0,2<----0,6<---------------0,3

=> m_Al = 0,2.27 = 5,4(g)

b) m_hh = 5,4 + 12,8 = 18,2(g)

c) \(C_{M\left(HCl\right)}=\dfrac{0,6}{0,3}=2M\)

\(n_{Zn} = a(mol) ; n_{Al} = b(mol) ; n_{Mg} = c(mol)\\ \Rightarrow 65a + 27b + 24c = 44,1(1)\\ Zn + 2HCl \to ZnCl_2 + H_2\\ 2Al + 6HCl \to 2AlCl_3 + 3 H_2\\ Mg + 2HCl \to MgCl_2 + H_2\\ n_{H_2} = a + 1,5b + c = \dfrac{31,36}{22,4} = 1,4(2)\\ Mà : 2a = 3b(3)\\ (1)(2)(3) \Rightarrow a = 0,3 ; b = 0,2 ; c = 0,8\\ \%m_{Zn} = \dfrac{0,3.65}{44,1}.100\% = 44,22\%\\ \%m_{Al} = \dfrac{0,2.27}{44,1}.100\% = 12,24\%\)

\(\%m_{Mg} = 100\% -44,22\% -12,24\% = 43,54\%\)

a) Gọi số mol của Mg là x, của Al là y \(\left(x,y>0\right)\)

Ta có: \(24x+27y=7,8\) (*) 

PTHH: 

\(Mg+H_2SO_4\rightarrow MgSO_4+H_2\uparrow\) (1)

\(2Al+3H_2SO_4\rightarrow Al_2\left(SO_4\right)_3+3H_2\uparrow\) (2)

 \(n_{H_2\left(1\right)+\left(2\right)}=\dfrac{9,916}{24,79}=0,4\left(mol\right)\)

Theo PTHH: \(n_{H_2\left(1\right)}=n_{Mg}=x\left(mol\right)\); \(n_{H_2\left(2\right)}=\dfrac{3}{2}n_{Al}=\dfrac{3}{2}y\left(mol\right)\)

\(\Rightarrow x+\dfrac{2}{3}y=0,4\) (**) 

Từ (*) và (**) ta có hệ: 

\(\left\{{}\begin{matrix}24x+27y=7,8\\x+\dfrac{3}{2}y=0,4\end{matrix}\right.\)

Giải hệ ta được: \(\left\{{}\begin{matrix}x=0,1\\y=0,2\end{matrix}\right.\)

\(\Rightarrow\%m_{Al}=\dfrac{27\cdot0,2\cdot100}{7,8}\approx69\%\)

\(\Rightarrow\%m_{Mg}=100\%-69\%=21\%\)

b) \(n_{MgSO_4}=n_{Mg}=0,1\left(mol\right)\); \(n_{Al_2\left(SO_4\right)_3}=\dfrac{1}{2}n_{Al}=0,1\left(mol\right)\)

Tổng khối lượng muối là:

\(m_{MgSO_4}+m_{Al_2\left(SO_4\right)_3}=0,1\cdot120+0,1\cdot342=46,2\)

a)

Gọi $n_{Mg} = a(mol) ; n_{Zn} = b(mol)$

Suy ra: $24a + 65b = 24,3(1)$
$n_{SO_2} = 0,5(mol)$

Bảo toàn electron : $2n_{Mg} + 2n_{Zn} = 2n_{SO_2}$
$\Rightarrow a + b = 0,5(2)$

Từ (1)(2) suy ra a = 0,2 ; b = 0,3

$m_{Mg} = 0,2.24 = 4,8(gam)$
$m_{Zn} = 0,3.65 = 19,5(gam)$
b)

Ta có :

$n_{H_2SO_4} = 2n_{SO_2} = 1(mol)$
$m_{H_2SO_4\ pư} = 1.98 = 98(gam)$

a) \(\left\{{}\begin{matrix}24.n_{Mg}+27.n_{Al}=6,93\\\dfrac{n_{Mg}}{n_{Al}}=\dfrac{4}{5}\end{matrix}\right.\)

=> \(\left\{{}\begin{matrix}n_{Mg}=0,12\left(mol\right)\\n_{Al}=0,15\left(mol\right)\end{matrix}\right.\)

=> \(\left\{{}\begin{matrix}m_{Mg}=0,12.24=2,88\left(g\right)\\m_{Al}=0,15.27=4,05\left(g\right)\end{matrix}\right.\)

b) 

PTHH: Mg + 2HCl --> MgCl₂ + H₂

            0,12->0,24

            2Al + 6HCl --> 2AlCl₃ + 3H₂

           0,15-->0,45

=> n_HCl(min) = 0,24 + 0,45 =0,69 (mol)

=> \(V_{dd.HCl\left(min\right)}=\dfrac{0,69}{4}=0,1725\left(l\right)\)