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Questions and Answers
What are redox reactions and what do they involve?
What are redox reactions and what do they involve?
Redox reactions involve the transfer of electrons between two species.
How can redox reactions be classified?
How can redox reactions be classified?
Redox reactions can be classified into two types: spontaneous and non-spontaneous.
What is the purpose of a galvanic cell?
What is the purpose of a galvanic cell?
A galvanic cell converts the energy released by a spontaneous redox reaction into electrical energy.
What occurs at the anode and cathode in a galvanic cell?
What occurs at the anode and cathode in a galvanic cell?
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Give an example of a spontaneous redox reaction in a galvanic cell.
Give an example of a spontaneous redox reaction in a galvanic cell.
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What is the main difference between a galvanic cell and an electrolytic cell?
What is the main difference between a galvanic cell and an electrolytic cell?
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What is the purpose of using an electrolyte in an electrolytic cell?
What is the purpose of using an electrolyte in an electrolytic cell?
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How does the direction of electron flow in an electrolytic cell compare to a galvanic cell?
How does the direction of electron flow in an electrolytic cell compare to a galvanic cell?
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What connects the two half-reactions in an electrolytic cell where the reactions occur in different containers?
What connects the two half-reactions in an electrolytic cell where the reactions occur in different containers?
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How is the electric current generated in an electrolytic cell?
How is the electric current generated in an electrolytic cell?
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Provide an example of a non-spontaneous redox reaction that occurs in an electrolytic cell.
Provide an example of a non-spontaneous redox reaction that occurs in an electrolytic cell.
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Explain the role of the external power source in an electrolytic cell.
Explain the role of the external power source in an electrolytic cell.
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Study Notes
Redox Reactions
Redox reactions, also known as oxidation-reduction reactions, involve the transfer of electrons between two species. These reactions can be classified into two types: spontaneous, which release energy (galvanic cells), and non-spontaneous, which require an external source of energy (electrolytic cells).
Galvanic Cells
A galvanic cell is a type of electrochemical cell that converts the energy released by a spontaneous redox reaction into electrical energy. This process is used to generate electricity, such as in batteries. The electrodes in a galvanic cell are connected by an electrolyte, which allows ions to transfer between the electrode compartments, thereby maintaining the system's electrical neutrality.
In a galvanic cell, the oxidation half-reaction occurs at one electrode (the anode), and the reduction half-reaction occurs at the other (the cathode). When the circuit is closed, electrons flow from the anode to the cathode, producing an electric current.
An example of a spontaneous redox reaction in a galvanic cell is the reaction between metallic zinc (Zn) and cupric ion (Cu2+) to produce copper metal (Cu) and zinc ions (Zn2+). The balanced chemical equation is:
Zn(s) + Cu2+(aq) → Cu(s) + Zn2+(aq)
Electrolytic Cells
An electrolytic cell, on the other hand, consumes electrical energy from an external source to drive a non-spontaneous redox reaction. In this process, the electrolyte is used to deliver a direct current to the electrodes, causing a chemical reaction to occur. The direction of electron flow in an electrolytic cell may be reversed from the direction of spontaneous electron flow in a galvanic cell.
In an electrolytic cell, the two half-reactions are set up in different containers and are connected through the electrolyte, which is a salt bridge or a porous partition. The potential difference between the electrodes (voltage) causes electrons to flow from the reductant to the oxidant, generating an electric current.
An example of a non-spontaneous redox reaction in an electrolytic cell is the decomposition of molten sodium chloride (NaCl) into sodium metal (Na) and chlorine gas (Cl2). The reaction is written as:
2 NaCl(l) → 2 Na(s) + Cl2(g)
In this case, electrons from the negative terminal of an external power source flow to the cathode, where they are used to reduce sodium ions (Na+) into sodium metal (Na).
Both galvanic and electrolytic cells are essential in the field of electrochemistry, as they allow for the conversion of chemical energy into electrical energy, or vice versa, depending on the type of reaction.
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Description
Learn about redox reactions and the differences between galvanic cells (which convert energy from spontaneous redox reactions into electricity) and electrolytic cells (which use external energy to drive non-spontaneous redox reactions). Explore how electrons flow in each type of cell and see examples of redox reactions in galvanic and electrolytic cells.
