Comprehensive knowledge accumulation in chemistry
1 The most closely related to the chemical properties of elements is the outermost electron number of atoms.
The most abundant element in the earth's crust is oxygen, and the most abundant metal element is aluminum. The chemical formula of the substance formed by the combination of the most nonmetallic elements and the most metal elements in the earth's crust is Al2O3.
3 If the number of protons in a nucleus is 19 and the number of neutrons is 20, the number of electrons outside the nucleus is 19, and its relative atomic proton mass is 39.
The calligraphy and paintings written or painted by some ancient painters can be preserved for a long time because the chemical properties of carbon are relatively stable at room temperature.
A group of substances with similar physical and chemical properties are H2 and carbon monoxide.
The gases that can be collected by exhaust method are CO2, H2 and O2, while the gases that cannot be collected by exhaust method are CO. ..
A bus was driving on the expressway at night, and it found that the oil tank leaked and the carriage was full of gasoline smell. The emergency measures to be taken at this time are to open all windows, prohibit all fireworks and evacuate passengers.
The principle of extinguishing alcohol lamp with lamp holder is to isolate air. Wood fires are often put out with water, and the main function of water is to lower the temperature below the ignition point.
The reasonable explanation for the phenomenon that charcoal burns more violently in pure oxygen than in air is that pure oxygen has better combustion-supporting property than air; The reason why honeycomb coal burns more easily than lump coal is that many small holes in honeycomb coal make honeycomb contact with oxygen better.
10 The three major fossil fuels widely used in the world today are oil, natural gas and coal; The harmful gases that cause air pollution mainly refer to carbon monoxide, sulfur dioxide and nitric oxide.
1 1 The simplest physical method to distinguish alcohol from water is smell, and the simplest chemical method is ignition.
12 purification operation sequence of crude salt containing a small amount of sediment: dissolution, filtration, evaporation and crystallization.
13 soft water refers to water that contains no or only a small amount of calcium and magnesium salts, such as rainwater. Hard water refers to water containing more calcium and magnesium salts, which tastes bad and is easy to form scale. Hard water and soft water can be distinguished by soapy water.
14 pure and bright black iron wire is put into blue copper sulfate solution, and the iron wire is taken out later, and its surface is covered with a layer of red substance. The chemical equation of the reaction is Fe+CuSO4 = = = Cu+FeSO4.
15 the reason why bordeaux mixture can't be prepared in iron containers. (Bordeaux mixture is composed of copper sulfate and hydrated lime. )
Reason: Iron will undergo displacement reaction with copper sulfate, which will deteriorate Bordeaux solution. Fe+cuso 4 = = = = Cu+feso 4
16 principle of copper hydrometallurgy in early Song Dynasty in China: Fe+CuSO4 = = = Cu+FeSO4.
The flame of 17 alcohol lamp can be divided into flame core, internal flame and external flame, with the external flame having the highest temperature.
18 in the experiment of burning pure iron in oxygen, a small amount of water or fine sand should be filled at the bottom of the bottle in advance to prevent the product from splashing after melting and cracking at the bottom of the bottle.
In the experiment of 19, if the dosage of the drug is not specified, it is usually taken according to the minimum amount: 1 ~ 2 ml of liquid, and only the bottom of the test tube needs to be covered with solids.
Tungsten is used as the filament in the bulb because it has a high melting point and is not easy to melt.
The main difference between 2 1 pig iron and steel is that the main component of pig iron and steel is iron, but the carbon content is different and the properties are different.
22 Method of removing a small amount of copper sulfate impurities from ferrous sulfate: add excessive iron filings (enlarge contact surface) into ferrous sulfate solution mixed with a small amount of copper sulfate impurities, and filter after full reaction. The residue is a mixture of copper and iron, and the filtrate is ferrous sulfate solution.
The reason why copper is easy to rust in humid air: In humid air containing carbon dioxide, the copper surface is rusty and porous, which makes the copper inside continue to be corroded. 2Cu + O2 + H2O + CO2 ==== Cu2(OH)2CO3
24 Methods for rapidly dissolving potassium nitrate solid in water: ① Grinding potassium nitrate into powder; (2) constantly stirring with a glass rod; ③ Increase the temperature.
25 physiological saline: it is a sodium chloride solution with 0.9% solute mass fraction.
The methods to change a bottle of nearly saturated potassium nitrate solution into saturated solution include cooling, adding solute and evaporating solvent at constant temperature.
When boiling water, many bubbles appear at the bottom of the pot soon after heating, indicating that the solubility of gas decreases with the increase of temperature. When the soda bottle cap is opened, a large number of bubbles escape from the bottle mouth, which is because the pressure decreases and the gas solubility decreases.
When the crude salt is dissolved, it must be stirred with a glass rod to accelerate the dissolution. When the filtrate is evaporated, it must be constantly stirred with a glass rod to prevent droplets from splashing due to local overheating of the liquid. When there are a lot of solids in the evaporating dish, stop heating to avoid burning the solids.
29 put salt solids in a bottle opener for a long time, and the quality is generally unchanged.
To distinguish dilute hydrochloric acid from dilute sulfuric acid, it is best to use BaCl2 reagent, and be careful not to use AgNO3.
3 1 in the laboratory, sodium hydroxide solid needs to be sealed and preserved because it is easy to deliquesce and absorbs carbon dioxide in the air.
The operation method of measuring the pH value of the solution to be tested with pH test paper is as follows: immerse the dry and clean glass rod in the solution to be tested, dip it on the pH test paper, and compare it with the colorimetric plate to read the pH value.
When opening the reagent bottle containing concentrated hydrochloric acid, white fog appeared on the bottle mouth. This phenomenon can be summarized as follows:
(1) concentrated hydrochloric acid is volatile. (2) HCl is soluble in water.
Alum 34 is a good water purifier, which can be used to purify domestic drinking water. Its chemical formula is KAl(SO4)2? 6? 1 12H2O .