Методическая разработка по английскому языку для студентов факультета химии и химической технологии " Simple Chemistry" Алматы 2017
Ex. 1 Read and translate the text
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мет. разработка по химии
| Ex. 1 Read and translate the text
Electrolysis Electrolysis is a technique that uses a direct electric current (DC) to force non-spontaneous chemical reaction to occur. This is achieved when two electrodes are submersed in an electrically conductive solution, and the electrical voltage which is applied to the two electrodes increases until electrons flow. The electrode which receives the electrons, or where the reduction reactions occur, is called the cathode. The electrode which supplies the electrons, or where the oxidation reactions occur, is called the anode. A molten salt is an example of something that may be electrolyzed because salts are composed of ions. When the salt is in its solid state, the ions cannot freely move. However, when the salt is heated enough until it melts, the ions are free to move. This mobility of the ions in the molten salt makes the salt electrically conductive. In the electrolysis of a molten salt, for example melted N aCl, the cation of the salt (in this case Na+) will be reduced at the cathode, and the anion of the salt (in this case Cl−) will e oxidized at the anode: Cathode reaction: Na+ + e- → Na Anode reaction: 2Cl → Cl2 + 2 e- Aqueous solutions of salts can be also electrolyzed because they are also electrically conductive. In aqueous solutions, there is an additional reaction possible at the cathode and the anode: Cathode: 2 H2O + 2 e- → H2 + 2 OH- (reduction of water) Anode: 2 H2O → 4 H+ + O2 + 4 e- (oxidation of water) With the addition of these two reactions, there are now two possible reactions at each electrode. At the cathode, either the reduction of the cation or the reduction of water will occur. At the anode, either the oxidation of the anion or the oxidation of water will occur. The following rules determine which reaction takes place at each electrode: Cathode: If the cation is a very active metal, water will be reduced. Very active metals include Li, Na, K, Rb, Cs, Ca, Sr, and Ba. If the cation is an active or inactive metal, the cation will be reduced. Anode: If the anion is a polyatomic ion, water will generally be oxidized. Specifically, sulfate, perchlorate, and nitrate ions are not oxidized. жүктеу/скачать 422,31 Kb. Достарыңызбен бөлісу:
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