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An automated external defibrillator (AED) is a medical device used to send an electric shock to the heart after cardiac arrest. A key component of the AED is the power source, or battery. Batteries used in AEDs need to have a good charge-to-weight ratio; they must be safe and reliable as well as rechargeable.Two types of rechargeable batteries used in early models of AEDs are the lead storage (also called lead-acid) battery and the nickel-cadmium (NiCd) battery. These batteries consist of multiple electrochemical cells that are connected in series to deliver a potential between 9 V and 18 V. A capacitor allows the AED to accumulate charge so that it can deliver between 300 V and 1,000 V.Some AEDs use a sealed lead storage battery. Lead storage batteries are robust and hold a charge for a long time. However, they have a low energy-to-weight ratio. Each lead storage cell delivers approximately 2.0 V, and a battery of four cells weighing 1000 g can provide 30 W∙h of energy.
Figure 1 Electron flow in a lead storage battery when discharging and chargingThe half reactions for the anode and cathode of a lead storage battery in 4 M of sulfuric acid (H₂SO₄) are shown in Reactions 1 and 2:
Reaction 1
Reaction 2
NiCd batteries have a higher energy-to-weight ratio than lead storage batteries but cannot hold as much charge. Each NiCd cell delivers approximately 1.3 V, and a single-cell battery weighing 120 g can provide 7.2 W∙h of energy.The half reactions at the anode and cathode for a NiCd battery in KOH are shown in Reactions 3 and 4:
Reaction 3

Reaction 4
-Would the concentration of H₂SO₄ remain constant as a lead storage battery is discharged?

Question

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An automated external defibrillator (AED) is a medical device used to send an electric shock to the heart after cardiac arrest. A key component of the AED is the power source, or battery. Batteries used in AEDs need to have a good charge-to-weight ratio; they must be safe and reliable as well as rechargeable.Two types of rechargeable batteries used in early models of AEDs are the lead storage (also called lead-acid) battery and the nickel-cadmium (NiCd) battery. These batteries consist of multiple electrochemical cells that are connected in series to deliver a potential between 9 V and 18 V. A capacitor allows the AED to accumulate charge so that it can deliver between 300 V and 1,000 V.Some AEDs use a sealed lead storage battery. Lead storage batteries are robust and hold a charge for a long time. However, they have a low energy-to-weight ratio. Each lead storage cell delivers approximately 2.0 V, and a battery of four cells weighing 1000 g can provide 30 W∙h of energy.

Figure 1 Electron flow in a lead storage battery when discharging and chargingThe half reactions for the anode and cathode of a lead storage battery in 4 M of sulfuric acid (H₂SO₄) are shown in Reactions 1 and 2:

Reaction 1

Reaction 2
NiCd batteries have a higher energy-to-weight ratio than lead storage batteries but cannot hold as much charge. Each NiCd cell delivers approximately 1.3 V, and a single-cell battery weighing 120 g can provide 7.2 W∙h of energy.The half reactions at the anode and cathode for a NiCd battery in KOH are shown in Reactions 3 and 4:

Reaction 3

Reaction 4
-Would the concentration of H₂SO₄ remain constant as a lead storage battery is discharged?

Quizplus · Accepted Answer

11ecba2d_11b8_058b_a3bf_1b29e6c732ab_MD0008_00 When a lead storage battery is discharged, lead oxide (PbO₂) gains electrons, or is reduced. Based on the oxidation-reduction reactions for the lead storage battery, water is one of the products from the reduction of PbO₂. This oxidation-reduction reaction occurs in an acidic medium. Before discharging, the concentration of H₂SO₄ is 4 M, but after the battery is completely discharged, the acid is diluted by the additional water, lowering the concentration of H₂SO₄. Because the concentration of H₂SO₄ changes when the battery is discharged, it is often used as an indicator of when the battery needs to be charged. (Choice B) The concentration of PbSO₄ increases as the battery is discharged, which requires SO₄²⁻ ions to come out of solution. This decreases the concentration of H₂SO₄. (Choice C) It is true that the concentration of H₂SO₄ does not remain constant; however, the SO₄²⁻ ion is not one of the species being oxidized or reduced. (Choice D) While it is true that the H⁺ ions are not oxidized or reduced, the H₂SO₄ concentration does not remain constant, since H⁺ ions (from H₂SO₄) are used in the formation of water during the reduction half-reaction. Educational objective: A lead storage battery is an example of an oxidation-reduction reaction that occurs in an acidic electrolyte. Because water is one of the products of the reaction, the acidic electrolyte will be diluted as the battery discharges.

Passage An Automated External Defibrillator (AED) Is a Medical Device Used