Tuesday, October 7, 2008

electrolysis- notes

* Electrolysis is the process of splitting substances by passing electricity.

* Electrolysis involves the passage of an electric current through an ionic substance that is either molten or dissolved in a suitable solvent, resulting in chemical reactions at the electrodes.

* Electrodes are metals used for electrical contact. The positive electrode is called the anode and the negative electrode is called the cathode. To be useful for electrolysis, the electrodes need to be able to conduct electricity, and metal electrodes are generally used. Graphite electrodes and semiconductor electrodes are also used.

* An ionic compound, or compound that reacts with solvent to produce ions (such as an acid) is dissolved in an appropriate solvent, or an ionic compound is melted by heat.

* Each electrode attracts ions that are of the opposite charge. Therefore, positively charged ions (called cations) move towards the electron-emitting (negative) cathode, whereas negatively-charged ions (called anions) move towards the positive anode.

* Electrolytes are substances which can be split by passing electricity. They are usually ionic compounds.
E.g.: NaCl, PbBr, etc …

* The energy required to separate the ions, and cause them to gather at the respective electrodes, is provided by an electrical power supply. At the electrodes, electrons are absorbed or released by the ions, forming a collection of the desired element or compound.

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chemistry notes / igcse-gcse- Olevel