Dry Cell vs. Button Cell

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Electrochemistry Homework Describe with the aid of labelled diagrams the structure and chemistry of a dry cell. Dry cells are electrochemical cells using a low-moisture electrolyte. They contain a centre of carbon rod, surrounded by an electrolyte paste and a zinc container. In the centre of most dry cells is a pure carbon rod (cathode) in the form of graphite. The carbon rod is surrounded by a layer of manganese dioxide (MnO2), and a thick paste of ammonium chloride (NH4Cl) and zinc chloride (ZnCl2), which serves as an electrolyte. The oxidation reaction that takes place on the zinc casing is: Zn(s)→Zn+2+2e- While the reduction reaction that takes place on the carbon rod is: 2MnO2+2H+(aq)+2e-→Mn2O3(s)+H2O(l) The overall reaction is: Zn(s)+2MnO2+2NH4+(s)→Mn2O3(s)+Zn(NH3)22+(aq)+H2O(l) The standard dry cell contains 1.5V. The reactions present in dry cells continue until they run out of a reactant (the anode or cathode). However, there are cells that can be recharged, as the redox reaction can be reversed in order to regenerate the original reactants. Some examples of these batteries include lithium batteries and car batteries. Compare it to a button cell or a lithium ion cells in terms of chemistry, cost and practicality, impact on society and environmental impact. Chemistry Dry cells contain a centre of a pure carbon rod that is surrounded by a layer of manganese dioxide (MnO2), and a thick paste of ammonium chloride (NH4Cl) and zinc chloride (ZnCl2). They undergo the oxidisation reaction of: Zn(s)→Zn+2+2e- And reduction reaction of: 2MnO2+2H+(aq)+2e-→Mn2O3(s)+H2O(l) Button cells are made up of an anode electrode of powdered zinc between two metal layers. The bottom of the cell and the casing make up the cathode electrode, and are made up of silver oxide (AgO) or mercury oxide (HgO) and graphite. They undergo the

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