Laboratory preparation method
1. heating potassium permanganate:
Heating potassium chlorate or potassium permanganate produces oxygen.
The thermal decomposition equation of potassium permanganate is controversial because its decomposition products will be different at different temperatures.
2. The heat of manganese dioxide and potassium chlorate: (The prepared oxygen contains a small amount of Cl2, O3 and ClO2；; This method has been deleted from some textbooks; The reaction is actually an exothermic reaction, not an endothermic reaction, and the above 1mol reaction occurs, and the exothermic reaction is 108kJ).
3. Catalytic decomposition of hydrogen peroxide solution (the catalyst is mainly manganese dioxide, and iron oxide and copper oxide can also be used)
Chemistry Poetry: Making Oxygen
The air tightness should be checked first in the experiment, and the test tube should be tilted evenly when heating.
Collect common drainage methods, first pull out the catheter and then move the lamp.
Explanation:
65438+ "Uniform heating" means that the test tube must be heated evenly when it is heated.
2. Common drainage collection method: refers to collecting oxygen by drainage gas collection method.
3. Pull out the catheter first and then move the lamp: it means that when oxygen production is stopped, the airway must be taken out of the water tank first, and then the alcohol lamp is taken out (if the alcohol lamp is pulled out first, water will be sucked into the hot test tube along the catheter due to the decrease of temperature and air pressure in the test tube, resulting in the rupture of the test tube due to rapid cooling).
Industrial law
1, liquid-air separation method
Low temperature and pressure make air become liquid and then evaporate. Because the boiling point of liquid nitrogen ‐ 196℃ is lower than that of liquid oxygen (‐ 183℃), nitrogen first evaporates from liquid air, and the rest is mainly liquid oxygen.
The main components in the air are oxygen and nitrogen. Using the different boiling points of oxygen and nitrogen, the process of preparing oxygen from air is called air separation. Firstly, the air is precooled and purified (removing a small amount of moisture, carbon dioxide, acetylene, hydrocarbons and other gases and dust and other impurities), and then compressed and cooled to make it liquid air. Then, using the boiling point difference between oxygen and nitrogen, the liquid air is evaporated and condensed for many times in the rectification tower, and oxygen and nitrogen are separated to obtain pure oxygen (purity can reach 99.6%) and pure nitrogen (purity can reach 99.9%). If some additional devices are added, rare inert gases such as argon, neon, helium, krypton and xenon can be extracted. The oxygen produced by the air separation unit is compressed by a compressor, and the finally compressed oxygen is stored in a high-pressure steel cylinder or directly transported to factories and workshops for use through pipelines. Although the production of oxygen by this method requires large complete sets of equipment and strict safe operation technology, the output is high, and thousands of cubic meters of oxygen can be produced every hour, and the raw materials consumed are just air that does not need to be purchased, transported and stored in warehouses. Therefore, since 1903 developed the first low-temperature air separation oxygen generator, this oxygen production method has been widely used.
2. Membrane separation technology
Membrane separation technology has developed rapidly. Using this technology, oxygen-enriched air with high oxygen content can be obtained by letting air pass through a film with oxygen-enriched function under a certain pressure. Using this membrane for multistage separation, oxygen-enriched air with oxygen content greater than 90% can be obtained.
3, molecular sieve oxygen method (adsorption method)
Using the characteristic that nitrogen molecules are larger than oxygen molecules, special molecular sieves are used to separate oxygen in the air. Firstly, the compressor forces dry air to enter the vacuum-pumping adsorber through the molecular sieve, so that nitrogen molecules in the air are adsorbed by the molecular sieve and oxygen enters the adsorber. When the oxygen in the adsorber reaches a certain amount (pressure reaches a certain level), the oxygen outlet valve can be opened to release oxygen. After a period of time, the nitrogen absorbed by molecular sieve gradually increased, the adsorption capacity weakened and the purity of oxygen produced decreased. The nitrogen adsorbed on the molecular sieve needs to be pumped out by a vacuum pump, and then the above process is repeated. This method of making oxygen is also called adsorption. A small adsorption oxygen generator is developed, which is convenient for home use.