Question

(a) Suggest an explanation for why liquid water is needed in an alkaline battery. (b) What is the advantage of using highly concentrated or solid reactants in a voltaic cell?

Short answer

(a) Liquid water is crucial in an alkaline battery because it acts as a solvent for the electrolyte, providing conductivity and a reaction medium for the redox reactions, as well as helping to maintain a stable temperature within the battery. (b) Using highly concentrated or solid reactants in a voltaic cell offers advantages such as increased energy capacity, longer shelf life, better safety, higher operating temperature range, and lower self-discharge rate.

Step-by-step solution

Part (a): Importance of Liquid Water in Alkaline Batteries

Alkaline batteries are electrochemical cells that generate electricity through a chemical reaction between a metal electrode and an electrolyte solution. The electrolyte in an alkaline battery typically consists of a basic (alkaline) solution, such as potassium hydroxide, dissolved in water. Liquid water is essential in an alkaline battery for the following reasons: 1. Conductivity: Water acts as a solvent for the electrolyte, which increases its conductivity by facilitating the movement of ions. The movement of ions is necessary for the flow of electric current in the battery. 2. Reaction medium: Water provides a suitable environment for the redox (reduction-oxidation) reactions to occur between the electrodes and the electrolyte. These redox reactions are responsible for the production of electrical energy in batteries. 3. Stability: The presence of water helps to maintain a stable temperature within the battery, as water can absorb or release heat during the chemical reactions. This ensures efficient performance and longer life of the battery.

Part (b): Advantages of using Highly Concentrated or Solid Reactants in a Voltaic Cell

A voltaic cell, also known as a galvanic cell, is an electrochemical cell that converts the chemical energy of redox reactions into electrical energy. Using highly concentrated or solid reactants in a voltaic cell offers the following advantages: 1. Increased energy capacity: Highly concentrated or solid reactants tend to have a higher energy density compared to their diluted counterparts. This means they can store more energy in a smaller volume, which results in higher capacity cells. 2. Longer shelf life: Solid reactants and concentrated electrolytes are less prone to evaporation or leakage, resulting in a longer shelf life for the voltaic cell. 3. Better safety: Solid reactants and concentrated electrolytes are generally more stable, thereby reducing the risk of accidents caused by spills, leaks, or other chemical reactions. In addition, solid or semi-solid electrolytes can provide a safer alternative to liquid electrolytes, which are more prone to short-circuit and other safety issues. 4. Higher operating temperature range: Solid and highly concentrated reactants can offer a broader range of operating temperatures. This makes them more suitable for use in various environments and applications where temperature fluctuations might occur. 5. Lower self-discharge rate: Solid and highly concentrated reactants generally have a lower self-discharge rate compared to liquid-based reactants. This results in better energy retention over time, allowing the cells to maintain their charge for longer periods when not in use.