3Fe+2O₂\(\underrightarrow{t^0}\)Fe₃O₄

_{3............2............1...............(mol)}

0,2.....0,1.....0,06........(mol)

nFe=\(\dfrac{11,2}{56}=0,2\left(mol\right)\)

mFe₃O₄=0.06\(\times\)232=13,92(g)

VO₂=0,1.22,4=2,24 (l)

không phản ứng

Fe+2HCl\(\rightarrow\)FeCl₂+H₂

_{1..........2..............1.........1................(mol)}

0,1.....0,2........0,1.....0,1..........(mol)

200ml=0,2l

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

Khí B: khí H₂

C_MHCl=\(\dfrac{n}{V}=\dfrac{0,2}{0,2}=1M\)

2NaOH+FeCl₂\(\rightarrow\)Fe(OH)_{2\(\downarrow\)}+2NaCl

2...............1................1..............2...........(mol)

................0,1...............0,1........................(mol)

Fe(OH)₂\(\underrightarrow{t^o}\)FeO+H₂O

1....................1......1............(mol)

0,1.................0,1.................(mol)

mFeO=\(0,1.72=7,2\left(g\right)\)

a) Tác dụng chỉ thị màu

quỳ tím\(\underrightarrow{ddCa\left(OH\right)_2}\) xanh

phenolphtalein\(\underrightarrow{ddCa\left(OH\right)_2}\) đỏ

(không màu)

b) Tác dụng với axit\(\rightarrow\)muối canxi

\(Ca\left(OH\right)_2+2HNO_3\rightarrow Ca\left(NO_3\right)_2+2H_2O\)

\(Ca\left(OH\right)_2+H_2SO_4\rightarrow CaSO_4+2H_2O\)

c) Tác dụng với oxit axit

\(CO_2+Ca\left(OH\right)_2\rightarrow CaCO_3+H_2O\)

d) Tác dụng với dung dịch muối\(\rightarrow\)muối natri+bazo mới

\(3NaOH+FeCl_3\rightarrow3NaCl+Fe\left(OH\right)_3\)

\(2NaOH+Mg\left(NO_3\right)_2\rightarrow2NaNO_3+Mg\left(OH\right)_2\)

b) \(\left(x-2\right)\left(x^2-2x+4\right)-x\left(x^2+2\right)=15\)

\(x^3-8-x^3-2x=15\)

\(-2x=23\Rightarrow x=\dfrac{-23}{2}\)

Bài 2: \(a.x^2-y^2=\left(x-y\right)\left(x+y\right)=\left(87-13\right)\left(87+13\right)=74.100=7400\)

b. \(x^3-3x^2+3x-1=\left(x^3-1\right)-\left(3x^2-3x\right)\)

\(x^2\left(x-1\right)-3x\left(x-1\right)=\left(x-1\right)\left(x^2-3x\right)\)

tại x=101, ta có:

\(\left(101-1\right)\left(101^2-3.101\right)=989800\)

1. \(\left(x+5\right)\left(x^2-5x+25\right)-\left(x-2\right)\left(x^2+2x+4\right)\)

\(=x^3+125-\left(x^3-8\right)=x^3+125-x^3+8=133\)

a) \(101^2=\left(100+1\right)^2=100^2+2.100.1+1^2=10201\)

b) \(199^2=\left(100+99\right)^2=100^2+2.100.99+99^2=39601\)

c) \(47.53=\left(50-3\right)\left(50+3\right)=50^2-3^2=2491\)