Redox Reaction Notes

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Chapter 18 Notes The Reactivity of Metals When an iron nail is left in copper sulfate solution a reaction occurs, the iron removes the copper from solution. This is a displacement reaction. The iron is more reactive than the copper. We know from experience that different metals have varying abilities to react with other substances. Eg. Metals can be put in a reactivity list which is called the reactivity series of metals or the activity series. Table 18.1 Reactivity of metals and the periodic table. The metals in groups I and II are very reactive. Metals tend to act as reductants. The reactivity of metals tends to decrease across the periodic table and down the group. You can use the reactivity series to predict redox reactions. ELECTROCHEMICAL CELLS Redox reactions that occur spontaneously can be used to produce energy. The energy can be released as heat, light, electricity or sound depending on the set-up of the displacement reaction. Eg. Iron nail in copper sulfate solution produces heat energy. If the reactions are separated the electrons can be forced to move through wires to create an electrical current. This is the set-up in batteries. Such set-ups are called ELECTROCHEMICAL CELLS. Their function is to be an energy converter, changing chemical energy into electrical energy. A simple electrochemical cell consists of: • Two half-cells, containing two electrodes (anode and cathode) and two electrolytes • A conducting wire • A salt bridge, containing another electrolyte. In half-cells the more reactive metal will always give its electrons to the ions of the less reactive metal. The ions of the less reactive metal will gain electrons from the other. THE ELECTRODE AT WHICH OXIDATION OCCURS IS CALLED THE ANODE. THE ELECTRODE AT WHICH REDUCTION OCCURS IS CALLED THE CATHODE. Key Knowledge questions.

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