CBSE 2024 · Region 1 · Set 1 · Q29 · 4 marks
Batteries and fuel cells are very useful forms of galvanic cell. Any battery or cell that we use as a source of electrical energy is basically a galvanic cell. However, for a battery to be of practical use it should be reasonably light, compact and its voltage should not vary appreciably during its use. There are mainly two types of batteries - primary batteries and secondary batteries. In the primary batteries, the reaction occurs only once and after use over a period of time the battery becomes dead and cannot be reused again, whereas the secondary batteries are rechargeable. Production of electricity by thermal plants is not a very efficient method and is a major source of pollution. To solve this problem, galvanic cells are designed in such a way that energy of combustion of fuels is directly converted into electrical energy, and these are known as fuel cells. One such fuel cell was used in the Apollo space programme. Answer the following questions :(a)How do primary batteries differ from secondary batteries ?(b)The cell potential of Mercury cell is $\displaystyle 1.35$ V, and remains constant during its life. Give reason.Write the reactions involved in the recharging of the lead storage battery.Write two advantages of fuel cells over other galvanic cells.
Batteries and fuel cells are very useful forms of galvanic cell. Any battery or cell that we use as a source of electrical energy is basically a galvanic cell. However, for a battery to be of practical use it should be reasonably light, compact and its voltage should not vary appreciably during its use. There are mainly two types of batteries - primary batteries and secondary batteries. In the primary batteries, the reaction occurs only once and after use over a period of time the battery becomes dead and cannot be reused again, whereas the secondary batteries are rechargeable. Production of electricity by thermal plants is not a very efficient method and is a major source of pollution. To solve this problem, galvanic cells are designed in such a way that energy of combustion of fuels is directly converted into electrical energy, and these are known as fuel cells. One such fuel cell was used in the Apollo space programme. Answer the following questions :
(a)
How do primary batteries differ from secondary batteries ?
(b)
The cell potential of Mercury cell is $\displaystyle 1.35$ V, and remains constant during its life. Give reason.
Write the reactions involved in the recharging of the lead storage battery.
Write two advantages of fuel cells over other galvanic cells.
Marking-scheme solution
(a) Primary batteries are not rechargeable while secondary batteries are rechargeable.
(b) Overall reaction does not involve any ion in solution whose concentration can change during its lifetime.
Cathode: \(\displaystyle \mathrm{PbSO}_{4}(\mathrm{~s})+2 \mathrm{e}^{-} \rightarrow \mathrm{Pb}(\mathrm{s})+\mathrm{SO}_{4}{ }^{2-}(\mathrm{aq})\) Anode: \(\displaystyle \mathrm{PbSO}_{4}(\mathrm{~s})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{PbO}_{2}(\mathrm{~s})+\mathrm{SO}_{4}{ }^{2-}(\mathrm{aq})+4 \mathrm{H}^{+}(\mathrm{aq})+2 \mathrm{e}^{-}\) OR(c) (i) More efficiency (ii) Pollution free
ElectrochemistryBatteriesUnderstandcase_studymedium
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CBSE Class 12 Chemistry past-paper question from the 2024board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.