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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
-If the electromotive force of the battery in an AED is found to be −2.0 V while it is charging, the battery is functioning as a:

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
-If the electromotive force of the battery in an AED is found to be −2.0 V while it is charging, the battery is functioning as a:

Quizplus · Accepted Answer

11ecba2d_11b5_bb91_a3bf_5f6d43788409_MD0008_00 The electromotive force E^o_cell for a cell is the difference between the standard reduction potential of the reaction at the cathode and the anode. The standard reduction potential of a particular metal or molecule is the potential (in volts) required to reduce the compound. The more negative the value of E^o for any given compound, the less likely it is to be reduced. The equation below is used to determine the standard potential for an oxidation-reduction pair for a particular electrochemical cell: 11ecba2d_11b5_bb92_a3bf_5fa7ce4bdf54_MD0008_00 For an electrolytic cell, this value is negative, indicating that the oxidation-reduction reaction is not spontaneous. During the charging phase of a rechargeable battery, an external potential is applied to force the oxidation-reduction reaction to proceed in a nonspontaneous direction. Because E^o_cell for this battery is a negative value (−2.0 V), the cell is functioning as an electrolytic cell. (Choice A) A galvanic cell is an electrochemical cell that converts chemical energy into electrical energy via an oxidation-reduction reaction. This reaction occurs spontaneously, and E^o_cell is a positive value. (Choice C) A concentration cell is a type of galvanic cell in which ions diffuse across a membrane, creating a potential. Because concentration is the driving force behind electron transfer, the standard potential of a concentration cell is positive whereas the concentration is different between the two compartments of the cell until it reaches equilibrium. (Choice D) A fuel cell is a type of galvanic cell whose reactants are continuously supplied at the anode and cathode, and whose products are continuously removed from the system. Although outside material is continuously supplied to the fuel cell, its reaction is still spontaneous, meaning that the E^o_cell is positive. Educational objective: When a battery is charging, it functions as an electrolytic cell because an external potential forces the oxidation-reduction reaction to proceed in a nonspontaneous direction. This makes the electromotive force for the cell a negative value.

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