a) 2KMnO₄ +16HCl --> 2KCl + 2MnCl₂ + 5Cl₂ + 8H₂O

Chất oxh: KMnO₄; chất khử: HCl

b) 8Al + 30HNO₃ --> 8Al(NO₃)₃ + 3N₂O + 15H₂O

31: 

\(n_{Fe}=\dfrac{5,6}{56}=0,1\left(mol\right)\)

PTHH: Fe + H₂SO₄ --> FeSO₄ + H₂

_____0,1----------------->0,1

10FeSO₄ + 2KMnO₄ + 8H₂SO₄ --> K₂SO₄ + 2MnSO₄ + 5Fe₂(SO₄)₃ + 8H₂O

=> nKMnO₄ = 0,02 (mol)

=> \(V=\dfrac{0,02}{0,5}=0,04\left(l\right)=40\left(ml\right)\)

30.

\(V_{\left(O;\dfrac{3}{4}\right)}\left(M\right)=M_1\Rightarrow\left\{{}\begin{matrix}x_1=\dfrac{3}{4}.4=3\\y_1=\dfrac{3}{4}.1=\dfrac{3}{4}\end{matrix}\right.\)

\(Q_{\left(O;-90^0\right)}\left(M_1\right)=M'\Rightarrow\left\{{}\begin{matrix}x'=y_1=\dfrac{3}{4}\\y'=-x_1=-3\end{matrix}\right.\)

\(\Rightarrow M'\left(\dfrac{3}{4};-3\right)\)

31.

\(cos\dfrac{x}{2}=-\dfrac{\sqrt{3}}{2}\Rightarrow\dfrac{x}{2}=\pm\dfrac{5\pi}{6}+k2\pi\)

\(\Rightarrow x=\pm\dfrac{5\pi}{3}+k4\pi\)

Nghiệm dương nhỏ nhất \(x=\dfrac{5\pi}{3}\Rightarrow a+b=5+3=8\)

  Câu 32 ạ

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