# Voltaic cells problems and solutions

1. What is a voltaic cell? Solution: A voltaic cell is a device in which a spontaneous redox reaction occurs that produces an electrical current. It consists of two half-cells connected by a wire and a salt bridge.

2. How does a voltaic cell produce electricity? Solution: A voltaic cell produces electricity by converting the chemical energy of a spontaneous redox reaction into electrical energy. The oxidation and reduction reactions occur in separate half-cells, creating a flow of electrons through the external circuit from the anode to the cathode.
3. What happens at the anode in a voltaic cell? Solution: The anode is where oxidation (loss of electrons) occurs in a voltaic cell. The species that loses electrons is oxidized and releases electrons into the external circuit.
4. What happens at the cathode in a voltaic cell? Solution: The cathode is where reduction (gain of electrons) occurs in a voltaic cell. The species that gains electrons from the external circuit is reduced at the cathode.
5. What is the function of the salt bridge in a voltaic cell? Solution: The salt bridge allows ions to flow between the half-cells to maintain electrical neutrality, which is necessary for the redox reaction to continue.
6. How do you calculate the cell potential of a voltaic cell? Solution: The cell potential (E°cell) of a voltaic cell is calculated by subtracting the standard reduction potential of the anode (E°ox) from the standard reduction potential of the cathode (E°red). E°cell = E°red – E°ox.
7. How does changing the concentrations of the reactants affect the cell potential? Solution: According to the Nernst equation, the cell potential will change with changes in the concentration of the reactants. As reactant concentration decreases, the cell potential decreases.
8. What happens to the cell potential when a voltaic cell reaches equilibrium? Solution: When a voltaic cell reaches equilibrium, the cell potential becomes zero because there is no longer a driving force for the redox reaction.
9. What is the difference between a primary and secondary voltaic cell? Solution: A primary cell is a voltaic cell in which the electrochemical reaction is not reversible. Once the reactants are consumed, the cell stops producing electricity. A secondary cell is a rechargeable voltaic cell where the electrochemical reaction can be reversed by applying an external current.
10. What is a common example of a voltaic cell? Solution: A common example of a voltaic cell is a battery. The most common type of battery, the alkaline battery, uses a reaction between zinc and manganese dioxide to produce a voltage.
11. Why does the voltage of a voltaic cell decrease over time? Solution: The voltage of a voltaic cell decreases over time as the reactants are consumed and their concentrations decrease. This reduces the driving force for the redox reaction, resulting in lower voltage.
12. How does temperature affect the cell potential? Solution: Temperature can affect the cell potential as described by the Nernst equation. If the reaction is endothermic, an increase in temperature will increase the cell potential, while if it is exothermic, an increase in temperature will decrease the cell potential.
13. Why are the electrodes in a voltaic cell made of different materials? Solution: The electrodes in a voltaic cell are made of different materials because each electrode needs to have a different affinity for electrons in order to create a potential difference. This difference is what drives the flow of electrons and generates an electric current.
14. What is a concentration cell? Solution: A concentration cell is a type of voltaic cell where the electrodes are the same material, but are in contact with solutions of different concentrations. The cell potential in a concentration cell is generated by the concentration gradient.
15. What is the standard cell potential? Solution: The standard cell potential is the potential difference between two half-cells under standard conditions, which are typically 1 M concentrations, 1 atm pressure, and 25°C temperature.
16. What is a fuel cell? Solution: A fuel cell is a type of voltaic cell that converts the chemical energy from a fuel into electricity. The fuel is typically oxidized at the anode and oxygen is reduced at the cathode.
17. How can you predict the spontaneity of a reaction using cell potential? Solution: If the cell potential (E°cell) is positive, the reaction is spontaneous. If the cell potential is negative, the reaction is non-spontaneous.
18. What is a half-cell? Solution: A half-cell is a structure that contains a conductive electrode and a surrounding conductive electrolyte separated by a naturally occurring Helmholtz double layer. Chemical reactions within this layer produce a potential difference across the layer, which can be harnessed in a voltaic cell.
19. What are the components of a Daniell cell? Solution: A Daniell cell is a type of voltaic cell composed of a copper cathode immersed in a copper(II) sulfate solution and a zinc anode immersed in a zinc sulfate solution, connected by a salt bridge.
20. How does a lead-acid battery work? Solution: A lead-acid battery is a type of secondary voltaic cell. It consists of a lead anode and a lead dioxide cathode submerged in sulfuric acid. When discharging, both electrodes react with the sulfuric acid to produce lead sulfate and water, producing a voltage. The reaction can be reversed by applying an external current to recharge the battery.