Passage
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
-To charge the NiCd cell, the applied external potential must be:

Question

Passage
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
-To charge the NiCd cell, the applied external potential must be:

Quizplus · Accepted Answer

11ecba2d_11b7_905a_a3bf_e780f50f4932_MD0008_00 Charging a battery involves forcing the oxidation-reduction reaction to run in a nonspontaneous direction by applying an external voltage. Any circuit has some amount of internal resistance that will deplete a portion of the applied voltage. Therefore, a higher voltage than that produced by discharging the battery is required to recharge it. The passage states that a NiCd battery produces a potential of 1.3 V, so the reverse reaction would require more than 1.3 V of applied potential to drive the reaction in the nonspontaneous direction. (Choice A) For the nonspontaneous reaction to occur, the applied potential must be greater than (not equal to) the potential that the oxidation-reduction reaction spontaneously produces when discharging. (Choices C and D) Although the electromotive force for a nonspontaneous reaction in an electrolytic cell is negative, the applied potential must be positive to overcome the negative potential of the reverse reaction. Educational objective: When charging a battery, an external potential must be applied to force the oxidation-reduction reaction in the nonspontaneous direction. The reverse reaction requires more than the potential produced by the battery because of internal resistance.

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