初中方程式 经典哦(国外英文资料).doc

初中方程式 经典哦(国外英文资料) Clarification of carbon dioxide gas in lime water Ca (OH) 2 + CO2, CaCO3 + H2O (metathesis): Phenomenon: Lime water is turbid by clarification Relevant knowledge: this reaction can be used to test the presence of carbon dioxide gas The magnesium band burns in the air 2Mg + O2 Phenomenon: produce a dazzling white light, producing white powder Relevant knowledge: (1) in this reaction, the magnesium elements change from free form to compound state; (2) the color of the material changes from silver white to white Water is broken down by electricity (or electrolysis of water) 2H2 = 2H2O + O2 = (decomposition) Phenomenon: a large number of bubbles are produced at the cathode and anode Related knowledge: (1) the anode produces oxygen, and the cathode produces hydrogen; (2) the volume ratio of hydrogen and oxygen is 2:1, and the mass ratio is 1:8. Quicklime and water reaction CaO + H2O = Ca (OH) 2 (combining) Phenomenon: white powder dissolves Related knowledge: (1) the name of the final solution obtained for calcium hydroxide solution, commonly known as clarifying lime; (2) in which drops into colorless phenolphthalein, phenolphthalein turns red; (3) lime is slaked lime is calcium oxide, calcium hydroxide. Copper powder is heated in the air 2Cu + O2 2CuO (combination) Phenomenon: the red substance gradually turns into black powder Relevant knowledge: This is an experiment for rough determination of the percent oxygen content in the air The laboratory produces oxygen (or a mixture of potassium chlorate and manganese dioxide) 2KClO3 + 3O2 = 2KCl (decomposition) Related knowledge: (1) in which the manganese dioxide as catalyst, generating speed of potassium chlorate decomposition rate or oxygen; (2) quality and chemical properties of manganese dioxide did not change in the chemical reaction; (3) after complete reaction, the residual solid in the test tube is a mixture of potassium chloride and manganese dioxide, separation the method is: dissolution, filtrat