Please do me a favor, a math problem, with equation solution! For a job, it takes 12 days for a to do it alone, and 20 days for B to do it alone. Now, after a few hours, the rest is done by B, and B completes it. If B does 4 days more than a, how many days has a done?
Let a do X days, then B do X + 4 days
x/12+(x+4)/20=1 8x/60+1/5=1 8x=48 x=6
How to write the corresponding data after writing the equation
Specifically refers to the calculation of a good equation, do not know the corresponding data should be written in which material below, the key point is specific
Chemical reaction
1. Combustion of magnesium in air: 2mg + O2 ignites 2MgO
2. Combustion of iron in oxygen: 3Fe + 2O2 ignites Fe3O4
3. Combustion of aluminum in air: 4Al + 3O2 ignites 2al2o3
4. Combustion of hydrogen in air: 2h2 + O2 ignites 2H2O
5. Combustion of red phosphorus in air: 4P + 5o2 ignites 2p2o5
6. Sulfur powder burning in air: S + O2 ignites SO2
7. Full combustion of carbon in oxygen: C + O2 ignites CO2
8. Incomplete combustion of carbon in oxygen: 2C + O2 ignites 2CO
9. Carbon dioxide passing through hot carbon layer: C + CO2 high temperature 2CO
10. Combustion of carbon monoxide in oxygen: 2CO + O2 ignites 2co2
11. Reaction of carbon dioxide and water (carbon dioxide into purple litmus test solution): CO2 + H2O = = = H2CO3
12. Quicklime dissolved in water: Cao + H2O = = = Ca (OH) 2
13. Anhydrous copper sulfate as desiccant: CuSO4 + 5H2O = = = = CuSO4 · 5H2O
14. Combustion of sodium in chlorine: 2Na + Cl2 ignites 2nacl
decomposition reaction
15. Preparation of oxygen from hydrogen peroxide in laboratory: 2h2o2, MnO2, 2H2O + O2 ↑
16. Heating potassium permanganate: 2kmno4 heating k2mno4 + MnO2 + O2 ↑
17. Under the action of direct current, water is electrified by 2H2O, 2h2 ↑ + O2 ↑
18. The carbonic acid is unstable and separated into H2CO3 = = = H2O + CO2 ↑
19. High temperature calcined limestone (carbon dioxide industrial process): CaCO3 high temperature CaO + CO2 ↑
Displacement reaction
20. Reaction of iron with copper sulfate solution: Fe + CuSO4 = = FeSO4 + Cu
21. Reaction of zinc with dilute sulfuric acid (hydrogen production in laboratory): Zn + H2SO4 = = ZnSO4 + H2 ↑
22. Reaction of magnesium with dilute hydrochloric acid: Mg + 2HCl = = = MgCl2 + H2 ↑
23. Reduction of copper oxide by hydrogen: H2 + CuO heating Cu + H2O
24. Reduction of CuO by charcoal: C + 2CuO, high temperature 2Cu + CO2 ↑
25. Methane burning in air: CH4 + 2O2 ignites CO2 + 2H2O
26. Water vapor passes through the hot carbon layer: H2O + C, high temperature H2 + Co
27. Coke reduced iron oxide: 3C + 2fe2o3, high temperature 4Fe + 3co2 ↑
other
28. Reaction of sodium hydroxide solution with copper sulfate solution: 2naoh + CuSO4 = = Cu (OH) 2 ↓ + Na2SO4
29. Methane burning in air: CH4 + 2O2 ignites CO2 + 2H2O
30. Alcohol burning in air: C2H5OH + 3O2 ignites 2co2 + 3H2O
31. Reduction of copper oxide by carbon monoxide: CO + CuO heating Cu + CO2
32. Carbon monoxide reduced iron oxide: 3Co + Fe2O3, high temperature 2Fe + 3co2
33. Carbon dioxide: Ca (OH) 2 + CO2 = = = = CaCO3 ↓ + H2O
34. Reaction of sodium hydroxide with carbon dioxide (removal of carbon dioxide): 2naoh + CO2 = = = = Na2CO3 + H2O
35. Reaction of limestone (or marble) with dilute hydrochloric acid (laboratory preparation of carbon dioxide): CaCO3 + 2HCl = = = CaCl2 + H2O + CO2 ↑
36, sodium carbonate and concentrated hydrochloric acid reaction (foam extinguisher principle): Na2CO3 + 2HCl = = = 2NaCl + H2O + CO2
1、 Reaction of substance with oxygen:
(1) The reaction of elemental matter with oxygen is as follows
1. Combustion of magnesium in air: 2mg + O2 ignites 2MgO
2. Combustion of iron in oxygen: 3Fe + 2O2 ignites Fe3O4
3. Copper heated in air: 2Cu + O2 heated 2CuO
4. Combustion of aluminum in air: 4Al + 3O2 ignites 2al2o3
5. Combustion in hydrogen and air: 2h2 + O2 ignites 2H2O
6. Combustion of red phosphorus in air: 4P + 5o2 ignites 2p2o5
7. Sulfur powder burning in air: S + O2 ignites SO2
8. Full combustion of carbon in oxygen: C + O2 ignites CO2
9. Incomplete combustion of carbon in oxygen: 2C + O2 ignites 2CO
(2) Reaction of compound with oxygen:
10. Combustion of carbon monoxide in oxygen: 2CO + O2 ignites 2co2
11. Methane combustion in air: CH4 + 2O2 ignites CO2 + 2H2O
12. Alcohol burning in air: C2H5OH + 3O2 ignites 2co2 + 3H2O
2、 There are several decomposition reactions
13. Under the action of direct current, water is electrified by 2H2O, 2h2 ↑ + O2 ↑
14. Heating basic copper carbonate: Cu2 (OH) 2CO3 heating 2CuO + H2O + CO2 ↑
15. Heating potassium chlorate (with a small amount of manganese dioxide): 2kclo3 = = = = 2KCL + 3O2 ↑
16. Heating potassium permanganate: 2kmno4 heating k2mno4 + MnO2 + O2 ↑
17. Carbonic acid is not stable, but H2CO3 = = = H2O + CO2 ↑
18. High temperature calcined limestone: CaCO3, high temperature CaO + CO2 ↑
3、 There are several redox reactions
19. Reduction of CuO by hydrogen: H2 + CuO heating Cu + H2O
20. Reduction of CuO by charcoal: C + 2CuO, high temperature 2Cu + CO2 ↑
21. Reduction of iron oxide by coke: 3C + 2fe2o3, high temperature 4Fe + 3co2 ↑
22. Reduction of Fe3O4 by coke: 2C + Fe3O4, high temperature 3Fe + 2co2 ↑
23. Reduction of copper oxide by carbon monoxide: CO + CuO heating Cu + CO2
24. Reduction of iron oxide by carbon monoxide: 3Co + Fe2O3, high temperature 2Fe + 3co2
25. Reduction of Fe3O4 by carbon monoxide: 4Co + Fe3O4, high temperature 3Fe + 4co2
4、 The relationship among element, oxide, acid, alkali and salt
(1) Metal element + acid -------- Salt + hydrogen (displacement reaction)
26. Zinc and dilute sulfuric acid Zn + H2SO4 = ZnSO4 + H2 ↑
27. Iron and dilute sulfuric acid Fe + H2SO4 = FeSO4 + H2 ↑
28. Magnesium and dilute sulfuric acid Mg + H2SO4 = MgSO4 + H2 ↑
29. Aluminum and dilute sulfuric acid 2Al + 3h2so4 = Al2 (SO4) 3 + 3h2 ↑
30. Zinc and dilute hydrochloric acid Zn + 2HCl = = = ZnCl2 + H2 ↑
31. Iron and dilute hydrochloric acid Fe + 2HCl = = = FeCl2 + H2 ↑
32. Magnesium and dilute hydrochloric acid Mg + 2HCl = = = MgCl2 + H2 ↑
33. Aluminum and dilute hydrochloric acid 2Al + 6hcl = = 2alcl3 + 3h2 ↑
(2) Metal element + salt (solution) -- another metal + another salt
34. Reaction between iron and copper sulfate solution: Fe + CuSO4 = = = FeSO4 + Cu
35. Reaction between zinc and copper sulfate solution: Zn + CuSO4 = = = ZnSO4 + Cu
36. Reaction of copper with mercuric nitrate solution: Cu + Hg (NO3) 2 = = = Cu (NO3) 2 + Hg
(3) Alkaline oxide + acid -------- Salt + water
37. Reaction of iron oxide with dilute hydrochloric acid: Fe2O3 + 6hcl = = = 2fecl3 + 3H2O
38. Reaction of iron oxide with dilute sulfuric acid: Fe2O3 + 3h2so4 = = = Fe2 (SO4) 3 + 3H2O
39. Reaction of copper oxide with dilute hydrochloric acid: CuO + 2HCl = = = = CuCl2 + H2O
40. Reaction of copper oxide with dilute sulfuric acid: CuO + H2SO4 = = = = CuSO4 + H2O
41. Reaction of magnesium oxide with dilute sulfuric acid: MgO + H2SO4 = = = = MgSO4 + H2O
42. Reaction of calcium oxide with dilute hydrochloric acid: Cao + 2HCl = = = = CaCl2 + H2O
(4) Acid oxide + alkali salt + water
43. Deterioration of caustic soda exposed to air: 2naoh + CO2 = = = = Na2CO3 + H2O
44. Caustic soda absorbs sulfur dioxide: 2naoh + SO2 = = = = Na2SO3 + H2O
45. Caustic soda absorbs sulfur trioxide gas: 2naoh + SO3 = = = = Na2SO4 + H2O
46. Slaked lime metamorphoses in air: Ca (OH) 2 + CO2 = = = = CaCO3 ↓ + H2O
47. Absorption of sulfur dioxide by hydrated lime: Ca (OH) 2 + SO2 = = = = CaSO3 ↓ + H2O
(5) Acid + alkali salt + water
48. Hydrochloric acid reacts with caustic soda: HCl + NaOH = = = = NaCl + H2O
49. Reaction of hydrochloric acid and potassium hydroxide: HCl + KOH = = = = KCl + H2O
50. Reaction of hydrochloric acid and copper hydroxide: 2HCl + Cu (OH) 2 = = = = CuCl2 + 2H2O
51. Reaction of hydrochloric acid and calcium hydroxide: 2HCl + Ca (OH) 2 = = = = CaCl2 + 2H2O
52. Reaction of hydrochloric acid and ferric hydroxide: 3hcl + Fe (OH) 3 = = = = FeCl3 + 3H2O
53. Aluminum hydroxide in the treatment of gastric acidosis: 3hcl + Al (OH) 3 = = = = AlCl3 + 3H2O
54. Reaction of sulfuric acid and caustic soda: H2SO4 + 2naoh = = = = Na2SO4 + 2H2O
55. Reaction of sulfuric acid and potassium hydroxide: H2SO4 + 2koh = = = K2SO4 + 2H2O
56. Reaction of sulfuric acid and copper hydroxide: H2SO4 + Cu (OH) 2 = = = = CuSO4 + 2H2O
57. Reaction of sulfuric acid and ferric hydroxide: 3h2so4 + 2Fe (OH) 3 = = = Fe2 (SO4) 3 + 6H2O
58. Reaction of nitric acid and caustic soda: HNO3 + NaOH = = = = NaNO3 + H2O
(6) Acid + salt --- another acid + another salt
59. Reaction of marble with dilute hydrochloric acid: CaCO3 + 2HCl = = = CaCl2 + H2O + CO2 ↑
60. Reaction of sodium carbonate with dilute hydrochloric acid: Na2CO3 + 2HCl = = = 2nacl + H2O + CO2 ↑
61. Reaction of magnesium carbonate with dilute hydrochloric acid: MgCO3 + 2HCl = = = MgCl2 + H2O + CO2 ↑
62. Reaction of hydrochloric acid and silver nitrate solution: HCl + AgNO3 = = = AgCl ↓ + HNO3
63. Reaction of sulfuric acid and sodium carbonate: Na2CO3 + H2SO4 = = = Na2SO4 + H2O + CO2 ↑
64. Reaction of sulfuric acid and barium chloride solution: H2SO4 + BaCl2 = = = = BaSO4 ↓ + 2HCl
(7) Alkali + salt --- another alkali + another salt
65. Sodium hydroxide and copper sulfate: 2naoh + CuSO4 = = = = Cu (OH) 2 ↓ + Na2SO4
66. Sodium hydroxide and ferric chloride: 3naoh + FeCl3 = = = = Fe (OH) 3 ↓ + 3nacl
67. Sodium hydroxide and magnesium chloride: 2naoh + MgCl2 = = = = Mg (OH) 2 ↓ + 2nacl
68. Sodium hydroxide and copper chloride: 2naoh + CuCl2 = = = = Cu (OH) 2 ↓ + 2nacl
69. Calcium hydroxide and sodium carbonate: Ca (OH) 2 + Na2CO3 = = = CaCO3 ↓ + 2naoh
(8) Salt + salt -- two new salts
70. Sodium chloride solution and silver nitrate solution: NaCl + AgNO3 = = = = AgCl ↓ + NaNO3
71. Sodium sulfate and barium chloride: Na2SO4 + BaCl2 = = = BaSO4 ↓ + 2nacl
5、 Other reactions:
72. CO2 dissolved in water: CO2 + H2O = = = H2CO3
73. Quicklime dissolves in water: Cao + H2O = = = Ca (OH) 2
74. Sodium oxide dissolves in water: Na2O + H2O = = = = 2naoh
75. Sulfur trioxide dissolved in water: SO3 + H2O = = = = H2SO4
76. Heating CuSO4 · 5H2O, heating CuSO4 + 5H2O
77. Anhydrous copper sulfate as desiccant: CuSO4 + 5H2O = = = = CuSO4 · 5h2
Application of chemical equation reaction phenomenon
2mg + O2 ignites or Δ 2MgO burns violently. It produces bright white light, white solid, exothermic and a lot of white smoke and white signal bombs
Experiment on ignition of silver white liquid or Δ 2hgo by 2hg + O2 to form red solid lavasside
2Cu + O2 ignites or Δ 2CuO red metal becomes black solid
4Al + 3O2 ignites or Δ 2al2o3 silver white metal becomes white solid
3Fe + 2O2 ignites Fe3O4 to burn violently, Mars radiates all around, forms black solid, exothermic 4Fe + 3O2 and high temperature 2fe2o3
C + O2 ignites CO2 to burn violently, white light, release heat and make lime water turbid
S + O2 ignites SO 2 intense combustion, exothermic, pungent gas, light blue flame in air, and blue purple flame in oxygen
2h2 + O2 ignites the light blue flame of 2H2O, releases heat, and forms the liquid (water) high energy fuel which makes the anhydrous CuSO4 turn blue
4P + 5o2 ignites 2p2o5, which burns violently, gives off a lot of white smoke, and produces white solid, which proves the oxygen content in the air
CH4 + 2O2 ignites the blue flame of 2H2O + CO2, releases heat, and produces liquid (water) methane and natural gas which make lime water turbid and anhydrous CuSO4 blue
2c2h2 + 5o2 ignites the blue flame of 2H2O + 4co2, releases heat and black smoke, generates the liquid oxyacetylene flame which makes the lime water turbid and the anhydrous CuSO4 blue, and cuts the metal by welding
2kclo3mno2 Δ 2KCL + 3O2 ↑ generates the gas that reburnies the wood strips with Mars, and oxygen is prepared in laboratory
2kmno4 Δ k2mno4 + MnO2 + O2 ↑ turns purple to black, and produces the gas which makes the wood with Mars reburning. Oxygen is prepared in laboratory
The experimental results show that 2hgo Δ 2hg + O2 ↑ red changes to silvery white, and the formation of gas makes the wood with Mars reburning
When 2H2O is electrified, 2h2 ↑ + O2 ↑ water is electrified and decomposed into hydrogen and oxygen electrolyzed water
Cu2 (OH) 2CO3 Δ 2CuO + H2O + CO2 ↑ green turns black, there is liquid on the wall of the test tube, the limestone water becomes turbid, and the gas is heated by copper green