Question

The electrodes in a silver oxide battery are silver oxide \(\left(\mathrm{Ag}_{2} \mathrm{O}\right)\) and zinc. (a) Which electrode acts as the anode? (b) Which battery do you think has an energy density most similar to the silver oxide battery: a Li-ion battery, a nickel-cadmium battery, or a lead-acid battery? [ Section 20.7]

Short answer

(a) The anode in a silver oxide battery is the zinc electrode. (b) The Li-ion battery has an energy density most similar to the silver oxide battery.

Step-by-step solution

(Step 1: Identify oxidation and reduction reactions in the battery)

For the silver oxide battery, the reactions involved are: Oxidation (at anode): \(Zn \rightarrow Zn^{2+} + 2e^-\) Reduction (at cathode): \(Ag_2O + H_2O + 2e^- \rightarrow 2Ag + 2OH^-\) The electrode at which the oxidation reaction occurs is the anode, and the electrode at which the reduction reaction occurs is the cathode.

(Step 2: Determine the anode in the silver oxide battery)

According to the identified oxidation reaction in Step 1, zinc is getting oxidized, so the anode is the zinc electrode. Answer: (a) The anode in a silver oxide battery is the zinc electrode.

(Step 3: Compare energy density of silver oxide battery with other batteries)

The energy density of a battery refers to how much energy it can store per unit mass or volume. To determine which of the mentioned batteries has an energy density most similar to the silver oxide battery, we can compare their typical energy densities. 1. Silver oxide battery: Energy density is around 130 Wh/kg 2. Li-ion battery: Energy density ranges from 100 to 270 Wh/kg, with some newer ones even reaching 300 Wh/kg 3. Nickel-cadmium (Ni-Cd) battery: Energy density is about 40-60 Wh/kg 4. Lead-acid battery: Energy density ranges between 30 and 50 Wh/kg Answer: (b) Based on the comparison of energy densities, the Li-ion battery has an energy density most similar to the silver oxide battery.

Key concepts

Electrode Reactions in Silver Oxide Batteries

Electrode reactions are fundamental to understanding how batteries like the silver oxide battery operate. In a silver oxide battery, two chemical reactions occur at the electrodes during discharge. The anode reaction involves oxidation, where zinc loses electrons:

\(Zn \rightarrow Zn^{2+} + 2e^-\).

This transformation means the zinc electrode releases electrons into the circuit, which then flow to the cathode. On the flip side, the cathode reaction involves reduction, and in this case, silver oxide combines with water to accept electrons:

\(Ag_2O + H_2O + 2e^- \rightarrow 2Ag + 2OH^-\).

Here, silver oxide is reduced to silver metal, and the process generates hydroxide ions. The flow of electrons from the anode to the cathode through an external circuit is how electrical energy is supplied by the battery. Learning about these reactions provides a clear picture of the electrochemical processes that power devices. Grasping these electrode reactions can help students understand the foundational principles of battery chemistry and how different materials affect a battery's efficiency and capacity.

Energy Density Comparison of Common Batteries

Energy density is a crucial metric used to compare batteries, as it measures the amount of energy a battery can store relative to its weight or volume. A silver oxide battery has a notably high energy density, approximately 130 Wh/kg, which allows it to store a significant amount of energy in a small space and weight, benefiting portable electronics.

When comparing silver oxide batteries to other types, the differences in energy density become apparent:

• Li-ion batteries exhibit a wide energy density range from 100 to 270 Wh/kg, with cutting-edge models surpassing 300 Wh/kg.
• Nickel-cadmium batteries hold a lower energy density of about 40-60 Wh/kg.
• Lead-acid batteries, often used in automotive and backup power applications, have an energy density between 30 and 50 Wh/kg.

In terms of similarity, Li-ion batteries are the closest in energy density to silver oxide batteries, making them suitable for similar applications. Understanding energy density helps students evaluate why certain batteries are chosen for specific applications based on size, weight, and energy requirements.

Battery Electrochemistry

Battery electrochemistry involves the study of chemical processes that convert chemical energy into electrical energy in batteries. The reactions taking place at the electrodes, as seen in the silver oxide battery, are core components of these processes.

In a battery, electrochemical reactions are spontaneously driven by the difference in chemical potential between the two electrodes. This difference leads to the movement of electrons from the anode to the cathode through an external circuit, while ions move within the electrolyte to maintain charge balance.

A battery's performance, such as its voltage, capacity, and overall efficiency, depends on the materials used for the electrodes and the electrolyte, as well as how these materials interact. By analyzing these electrochemical properties, students can better understand how batteries store and release energy, as well as why some batteries outperform others across various applications.