1. 2FeO + 4H2SO4 _{đặc ,nóng} → Fe2(SO4)3  +  SO2 +​4H2O

 x1 | \(2Fe^{+2}\rightarrow Fe^{+3}_2+2e\)

x1  | \(S^{+6}+2e\rightarrow S^{+4}\)

2.  2Fe3O4 + 10H2SO4 _{đặc ,nóng} → 3Fe2(SO4)3 + SO2 + 10H2O

x1 | 2Fe₃^+8/3 \(\rightarrow\) 3Fe₂⁺³ + 2e

x1 | \(S^{+6}+2e\rightarrow S^{+4}\)

3. 2Fe(OH)2 + 4H2SO4 → Fe2(SO4)3 + SO2 + 6H2O

 x1 | \(2Fe^{+2}\rightarrow Fe^{+3}_2+2e\)

x1  | \(S^{+6}+2e\rightarrow S^{+4}\)

4. 2FeCO3 + 4H2SO4 → Fe2(SO4)3 + SO2 + 2CO2 + 4H2O

 x1 | \(2Fe^{+2}\rightarrow Fe^{+3}_2+2e\)

x1  | \(S^{+6}+2e\rightarrow S^{+4}\)

5. 2FexOy + (6x-2y)H2SO4 \(\rightarrow\) xFe2(SO4)3 + (3x-2y)SO2 + (6x-2y)H2O

x1          | 2Fe_x^+2y/x \(\rightarrow\) xFe₂⁺³ +(6x-4y)e
x(3x-2y) | \(S^{+6}+2e\rightarrow S^{+4}\)
 

What is there in front of your house?

Hoa learns languages badly.

\(\left\{{}\begin{matrix}3x+1< x-7\\1-2x>x+1\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}2x< -8\\3x< 0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x< -4\\x< 0\end{matrix}\right.\) \(\Rightarrow x< -4\)

Vậy nghiệm của hệ là \(S=\left(-\infty;-4\right)\)

\(\dfrac{1111\times5}{1515\times7}=\dfrac{1111\times5}{303\times5\times7}=\dfrac{1111}{2121}\)

\(=\dfrac{11\times101}{21\times101}=\dfrac{11}{21}\)

Câu 67:

Đổi 5,1 tấn = 5100 kg

Ta có: \(n_{NH_3}=\dfrac{5100}{17}=300\left(kmol\right)\)

Bảo toàn Nitơ: \(n_{NH_3}=n_{HNO_3\left(lý.thuyết\right)}=300\left(kmol\right)\)

\(\Rightarrow m_{ddHNO_3\left(thực\right)}=\dfrac{300\cdot40\%\cdot63}{63\%}=12000\left(kg\right)=12\left(tấn\right)\)

Câu 68:

Ta có: \(n_{HNO_3\left(thực\right)}=\dfrac{400\cdot12,6\%}{63}=0,8\left(mol\right)\) \(\Rightarrow n_{HNO_3\left(lý.thuyết\right)}=\dfrac{0,8}{40\%}=2\left(mol\right)\)

Bảo toàn Nitơ: \(n_{NH_3}=n_{HNO_3\left(lý.thuyết\right)}=2\left(mol\right)\) \(\Rightarrow V_{NH_3}=2\cdot22,4=44,8\left(l\right)\)

\(a,\Leftrightarrow6x^2-15x-6x^2+13x=12\\ \Leftrightarrow-2x=12\Leftrightarrow x=-6\\ b,\Leftrightarrow\left(x-1\right)\left(4x-7\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=1\\x=\dfrac{7}{4}\end{matrix}\right.\)