Ethanol generates ethylene and water under the condition of concentrated sulfuric acid 170 degrees celsius;
Second, the material:
Drugs: ethanol, concentrated sulfuric acid; Device: round bottom flask, thermometer, iron frame, sink, gas container, double-hole rubber stopper, alcohol lamp and catheter; Third, the steps:
Check the air tightness. Inject about 20 ml of mixed solution of ethanol and concentrated sulfuric acid into the flask, and put a few pieces of broken porcelain in the flask; Heating to rapidly raise the temperature to 170 DEG C, and dehydrating ethanol to generate ethylene; Collecting ethylene through drainage and gas collection; Then the gas is introduced into bromine water and acidic potassium permanganate solution respectively to observe the phenomenon; Pull out the catheter first, then turn off the light; Fourth, matters needing attention:
The volume ratio of ethanol to concentrated sulfuric acid in the reaction solution is 1∶3. Using excessive concentrated sulfuric acid can improve the utilization rate of ethanol and increase the output of ethylene; The purpose of adding a small amount of broken porcelain, zeolite or other inert solids to the round bottom flask is to prevent the reaction mixture from boiling when heated; The mercury ball of the thermometer should be inserted under the liquid surface to accurately measure the temperature of the reaction solution. When heating, the temperature should be quickly raised to 170℃ to reduce the chance of ether generation; In the reaction of preparing ethylene, concentrated sulfuric acid is used as catalyst, water absorbent and oxidant. In the process of reaction, ethanol is easily oxidized, and finally carbon dioxide, carbon monoxide, carbon and so on. At the same time, sulfuric acid itself is reduced to sulfur dioxide. Sulfur dioxide can discolor bromine water or potassium permanganate solution. Therefore, before the property experiment of ethylene, the gas should be removed with alkaline lime or the gas should be washed with 10% sodium hydroxide solution to remove sulfur dioxide, so as to obtain pure ethylene. If the air contains 3%, 4% to 34% ethylene, it is easy to explode when exposed to open fire, and the explosion degree is more violent than methane. So be careful when lighting ethylene.