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B) Evaluate the DRY CELL in comparison to a SILVER BUTTON CELL in terms of chemistry, cost and practicality, impact on society and environmental impact. DRY CELL SILVER BUTTON CELL Chemistry NEGATIVE TERMINAL: Zn --> Zn2+ + 2e- POSITIVE ELECTRODE: NH4+ + MnO2 + H2O + e- -->Mn(OH)3 + NH3 VOLTAGE: Approximately 1.50 volts ELECTROLYTE: NH4Cl and ZnCl2 paste ANODE: 2MnO2 (s) + H2O (l) + 2e- -->Mn2O3 (s) + 2OH- (aq) CATHODE: Ag2O(s) + H2O(l) + 2e- --> 2Ag(s) + 2OH-(aq) VOLTAGE: Approximately 1.55 volts ELECTROLYTE: KOH and Zn (OH)2 Cost & Practicality * Relatively inexpensive * Releases small voltage * Small and easy to store and use * Maintains constant voltage of a period of time * Not rechargeable * Short term uses only * Can not deliver high current * Battery may leak due to the zinc casing being used up in chemical reaction. * Short shelf life as acidic paste attacks the zinc casing USES: Toys, torches, portable radios * Expensive as it includes silver * Not rechargeable * Produces a significant amount of current * There is a constant voltage over a long period of time * Small size enables its use in delicate and portable devices. ...read more.


A paste of potassium hydroxide separates the two substances and acts as a porous medium. At the negative terminal the zinc oxides in an aqueous solution with hydroxide ions to form zinc oxide and water, whilst at the positive terminal silver oxide and water reduce to form silver solid and hydroxide ions. The cell has an overall voltage of 1.3V. Oxidation: 2MnO2 (s) + H2O (l) + 2e- -->Mn2O3 (s) + 2OH- (aq) Reduction: Ag2O(s) + H2O(l) + 2e- --> 2Ag(s) + 2OH-(aq) In terms of chemistry both cells differ greatly from the reactant to size and shape. The dry cell however has a slightly higher voltage than the silver button cell. Both cells have positives and negatives in relation to there cost and practicality. A positive aspect in both cells is that a voltage is maintained over a long period of time, a negative however is that in the dry cell this voltage is lower than in the button cell. The button cell can deliver high currents where as the dry cell can not. ...read more.


It would also have an impact on society as the workers who are exposed to the heavy metal and corrosive substances are more susceptible to developing abnormalities which can be fatal, such as cancer. Similarly in the button cell silver has major impacts on aquatic life. If was found the high levels of silver can lead to decreased major organ functions and is particularly lethal to aquatic plant species. The button cell also contains the corrosive substance potassium hydroxide which also causes abnormalities in organisms in high concentrations. In comparing the two cells in cost and practicality, impact on society and environmental impact, the silver cell has some important advantages over the dry cell. The silver button cell has much longer life than the dry cell. That is it can deliver a consistently higher voltage over a greater period of time, this is especially important in medical devices. The silver button cell is also less likely to leak thus less chance of having detrimental effects on the environment. Overall the silver button cell has the properties of the dry cell and other features which enables its use in a diverse range of situations. ...read more.

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