\(4-\dfrac{1}{4}-\dfrac{1}{28}-\dfrac{1}{70}-.....-\dfrac{1}{2002.2005}\)

\(=4-\left(\dfrac{1}{1.4}+\dfrac{1}{4.7}+\dfrac{1}{7.10}+.....+\dfrac{1}{2002.2005}\right)\)

\(=4-\left(1-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+.....+\dfrac{1}{2002}-\dfrac{1}{2005}\right)\)\(=4-\left(1-\dfrac{1}{2005}\right)\)

\(=4-1+\dfrac{1}{2005}=3+\dfrac{1}{2005}=\dfrac{6016}{2005}\)

a) 1. CaCO₃ →^to CaO + CO₂

2. CaO + H₂O → Ca(OH)₂

3. Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

b) 1. S + O₂ →^to SO₂

2. 2SO₂ + O₂ →^to 2SO₃

3. SO₃ + H₂O → H₂SO₄

4. H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O

1) 

• (1)Fe(NO3)₃ + NaOH => NaNO₃ + Fe(OH)₃ 
• (2)2Fe(OH)₃ =(t°)=> Fe₂O₃ + 3H₂O 
• (3) Fe₂O₃+ 6HCl => 2FeCl₃ +3H₂O 
• (4) FeCl₃ + 3AgNO₃ => Fe(NO3)₃ + 3AgCl 

2) 

• (1) 2Fe + 3Cl₂ => 2FeCl₃ 
• (2) FeCl₃ + 3NaOH => Fe(OH)₃ + 3NaCl 
• (3)2Fe(OH)₃ =(t°)=> Fe₂O₃ + 3H₂O 
• (4)Fe₂O₃ + 3H₂ =(t°)=2Fe + 3H₂O 
• (5)Fe + 2HCl => FeCl₂ + H₂ 
• (6)FeCl2 + 2AgNO3 => 2AgCl + Fe(NO₃)₂ 

a) S +O2(1)-> SO2

(2)2SO2+O2-> 2SO3

(3)SO3+H2O---> H2SO4

(4)H2SO4+2NaOH-> Na2SO4+2H2O

(5)Na2SO4+BaCl2----> BaSO4+2NaCl

b) 2Fe +3Cl2---->2FeCl3

(2)FeCl3+3NaOH-> Fe(OH)3 +3NaCl

(3)2Fe(OH)3----> Fe2O3+3H2O

(4)Fe2O3+3H2SO4--> Fe2(SO4)3+3H2O

(5)Fe2(SO4)3+6NaCl-> 2FeCL3+3Na2SO4

c) Fe +2HCl--> FeCl2+H2

(2)FeCl2+2AgNO3-> Fe(NO3)2 +2AgCl

(3)Fe(NO3)2+2NaOH----> Fe(OH)2 +2NaNO3

(4)Fe(OH)2+MgSO4---> FeSO4+Mg(OH)2

d) 4Al+3o2 ----> 2Al2O3

(2)Al2O3+3H2SO4---> Al2(SO4)3 +3H2O

(3)Al2(SO4)3+3BaCl2-> 2AlCl3 +3BaSO4

(4)AlCl3+3AgNO3----> Al(NO3)3 +3AgCl

(5)Al(NO3)3+3NaOH-> Al(OH)3 +3NaNO3

(6)2Al(OH)3-----> Al2O3+3H2O

e) 4Na +O2-> 2Na2O

(2)Na2O+H2O-> 2NaOH

(3)2NaOH+H2SO4-> Na2SO4+2H2O

(4)Na2SO4+BaCl2-> 2NaCl+BaSO4

(5)NaCl+AgNO3---> NaNO3+AgCl

Câu 1:

1. 4Fe + 3O₂ \(\underrightarrow{to}\) 2Fe₂O₃

2. Fe₂O₃ + 3H₂SO₄ → Fe₂(SO₄)₃ + 3H₂O

3. Fe₂(SO₄)₃ + 6NaOH → 3Na₂SO₄ + 2Fe(OH)₃

4. 2Fe(OH)₃ \(\underrightarrow{to}\) Fe₂O₃ + 3H₂O

5. Fe₂O₃ + 3H₂ \(\underrightarrow{to}\) 2Fe + 3H₂O

Câu 2:

1. 4Na + O₂ → 2Na₂O

2. Na₂O + H₂O → 2NaOH

3. 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O

4. Na₂SO₄ + BaCl₂ → 2NaCl + BaSO₄

=1/14 nha em

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