Lead Acid Battery Lead Acid Battery Lead–acid batteries, invented in 1859 by French physicist Gaston Planté, are the oldest type of rechargeable battery. Despite having a very low energy-to-weight ratio and a low energy-tovolume ratio, their ability to supply high surge currents means that the cells maintain a relatively large power-to-weight ratio. These features, along with their low cost, make them attractive for use in motor vehicles to provide the high current required by automobile starter motors. Lead–acid batteries (under 5 kg) account for 1.5% of all portable secondary battery sales in Japan by number of units sold (25% by price). Sealed lead–acid batteries accounted for 10% by weight of all portable battery sales in the EU in 2000. Sealed Lead Acid Battery :- The sealed lead acid battery has six cells mounted side by side in a single case. The cells are coupled together so that each 2.0V cells adds up to the 12.0 V overall battery. Lead-acid batteries are very heavy, but still much better than the light weight options, since lead acid batteries can deliver large surges of electricity needed to start a cold automobile engine. A fully charged lead-acid cell is made of a stack of alternating lead, Pb, and lead (IV) oxide, PbO2, plated isolated from each other by layers of porous separators.
Know More About :- Oxidation States
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All these parts sit in a concentrated solution of sulfuric acid. Inter cell connectors link the positive of one cell to the negative of the next cell, so the six cells are in a series. When the cell discharges, it acts as a galvanic cell. The following reactions occur: Negative: Pb(s) + HSO4 - + H2O(l) → 2e- + PbSO4(s) + H3O+(aq) Positive: PbO2(s) + HSO4 - (aq)+ 3H3O+(aq) + 2e- → PbSO4(s) +5 H2O(l) The lead sulfate is produced at both the electrodes. Also, two electrons are transferred in the overall reaction. The lead acid battery is housed in a thick plastic or rubber case. This prevents leakage of the corrosive sulfuric acid. The reactions both go to the right when current is being drawn from the battery. That is, lead (II) sulfate, PbSO4 is made at both the negative and positive plates. However, this happens by two different processes and for each mole of lead sulfate make two moles of electrons travel through the external circuit. These are the electrons, that, say for example- make the lights, indicators, and radio in the car work. When a car or lorry moves, an electric current is generated by the alternator. This current is passed into the battery in the direction that forces the two reactions to go to the left. That is, the lead sulfate is decomposed. In theory, at least, the charging and discharging can go on indefinitely. However, in practice, this is not so. A typical car battery provides a voltage of 12V. This is not a large voltage, but the battery can provide a large current, say 10A, without being destroyed.
Learn More :- Third Law of Thermodynamics
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2. The accuracy of titration will be high when the end point is quite close to the equivalence point. 3. For example in acid-base titration of a strong acid with a strong base, the equivalence point is at pH 7.00. 4. The indicator used for this titration is phenolphthalein which starts the color change at pH slightly above 8. 5. Hence, in this reaction the color change is noticed only when small excess amount added of titrant which introduces small positive error in the titration. 6. In other word both equivalence point and end point is different as equivalence point corresponds to the theoretical completion of the reaction while the endpoint is related to the actually measured physical change in the solution determined by an indicator or an instrument mentioned above.
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