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Questions and Answers
What is the fundamental process by which voltaic cells convert energy?
What is the fundamental process by which voltaic cells convert energy?
- Electromagnetic induction using magnetic fields.
- Nuclear fission reactions converting mass to energy.
- Spontaneous oxidation-reduction reactions converting chemical energy to electrical energy. (correct)
- Endothermic reactions absorbing heat and producing electricity.
Why is it essential to balance the movement of electrons in the external wire of a voltaic cell with the movement of ions in the solution?
Why is it essential to balance the movement of electrons in the external wire of a voltaic cell with the movement of ions in the solution?
- To prevent the electrodes from dissolving.
- To increase the rate of electron flow.
- To minimize heat generation within the cell.
- To maintain electrical neutrality and allow continuous operation of the cell. (correct)
What critical role does the carbon rod play in a zinc-carbon dry cell?
What critical role does the carbon rod play in a zinc-carbon dry cell?
- It serves as the cathode, facilitating the reduction of $MnO_2$ in the presence of $H_2O$. (correct)
- It acts as the anode where oxidation of zinc occurs.
- It prevents the electrolyte from leaking.
- It increases the internal resistance of the cell.
In an alkaline battery, what is the half-reaction that occurs at the anode?
In an alkaline battery, what is the half-reaction that occurs at the anode?
What distinguishes a mercury battery from a zinc-carbon dry cell or an alkaline battery regarding the anode half-reaction?
What distinguishes a mercury battery from a zinc-carbon dry cell or an alkaline battery regarding the anode half-reaction?
What unique feature defines a fuel cell compared to other voltaic cells such as dry cells or lead-acid batteries?
What unique feature defines a fuel cell compared to other voltaic cells such as dry cells or lead-acid batteries?
In the context of voltaic cells, what is the significance of the term 'galvanic cells'?
In the context of voltaic cells, what is the significance of the term 'galvanic cells'?
During the corrosion of iron, what role does oxygen play in the process?
During the corrosion of iron, what role does oxygen play in the process?
How does galvanizing prevent the corrosion of steel?
How does galvanizing prevent the corrosion of steel?
What is the purpose of using a 'sacrificial anode' in preventing corrosion?
What is the purpose of using a 'sacrificial anode' in preventing corrosion?
Which situation would most likely accelerate the corrosion of an iron object?
Which situation would most likely accelerate the corrosion of an iron object?
Why do alkaline batteries not have a carbon rod cathode?
Why do alkaline batteries not have a carbon rod cathode?
In a zinc-carbon dry cell, what happens to the zinc atoms at the negative electrode (anode)?
In a zinc-carbon dry cell, what happens to the zinc atoms at the negative electrode (anode)?
What is the overall net reaction in a fuel cell that uses hydrogen and oxygen as reactants?
What is the overall net reaction in a fuel cell that uses hydrogen and oxygen as reactants?
Why are fuel cells considered to have very low emissions?
Why are fuel cells considered to have very low emissions?
Which of the following metals is commonly used as a sacrificial anode to prevent corrosion of iron or steel structures?
Which of the following metals is commonly used as a sacrificial anode to prevent corrosion of iron or steel structures?
In the context of corrosion, what is the role of water?
In the context of corrosion, what is the role of water?
Which type of voltaic cell uses a carbon rod as the cathode?
Which type of voltaic cell uses a carbon rod as the cathode?
What is the chemical formula for rust, which forms during the corrosion of iron?
What is the chemical formula for rust, which forms during the corrosion of iron?
What is the purpose of a porous barrier in a galvanic cell?
What is the purpose of a porous barrier in a galvanic cell?
Flashcards
What are voltaic cells?
What are voltaic cells?
Cells that use spontaneous oxidation-reduction reactions to convert chemical energy into electrical energy.
How do Voltaic Cells work?
How do Voltaic Cells work?
A type of voltaic cell where electrons given up at the anode pass along an external connecting wire to the cathode.
What is a Dry cell?
What is a Dry cell?
A voltaic cell that includes zinc-carbon, alkaline and mercury batteries.
Zinc-Carbon Dry Cell Anode
Zinc-Carbon Dry Cell Anode
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Alkaline Battery Cathode
Alkaline Battery Cathode
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Definition of a Fuel Cell
Definition of a Fuel Cell
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What is galvanizing?
What is galvanizing?
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What is Cathodic protection?
What is Cathodic protection?
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What is a Sacrificial Anode?
What is a Sacrificial Anode?
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Corrosion
Corrosion
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During corrosion what happens to oxygen?
During corrosion what happens to oxygen?
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Study Notes
- Voltaic cells use spontaneous oxidation-reduction reactions
- Voltaic cells are also called galvanic cells
- Batteries are the most common application of voltaic cells
How Voltaic Cells Work
- Electrons given up at the anode pass along the external connecting wire to the cathode
- The movement of electrons through the wire must be balanced by the movement of ions in the solution
- Dry cells are voltaic cells
- The three most common types of dry cells are zinc-carbon battery, the alkaline battery, and the mercury battery
How Voltaic Cells Work: Zinc-Carbon Dry Cells
- Batteries such as those used in flashlights are zinc-carbon dry cells
- Zinc atoms are oxidized at the negative electrode, or anode according to:
- Zn(s) → Zn2+(aq) + 2e-
- The carbon rod is the cathode or positive electrode
- MnO2 is reduced in the presence of H2O according to:
- 2MnO2(s) +H2O(l) + 2e- → Mn2O3(s) + 2OH¯(aq)
How Voltaic Cells Work: Alkaline Batteries
- Alkaline batteries do not have a carbon rod cathode, allowing them to be smaller
- The half-reaction at the anode is:
- Zn(s) + 2OH → Zn(OH)2 (aq) + 2e¯
- The reduction at the cathode is the same as that for the zinc-carbon dry cell
How Voltaic Cells Work: Mercury Batteries
- The anode half-reaction is identical to that found in the alkaline dry cell.
- The cathode half-reaction is:
- HgO(s) + H₂O(l) + 2e¯ → Hg(/) + 2OH¯(aq)
How Voltaic Cells Work: Fuel Cells
- A fuel cell is a voltaic cell in which the reactants are being continuously supplied and the products are being continuously removed
- Cathode reaction: O2(g) + 2H2O(l) + 4e- → 4OH-(aq)
- Anode reaction: 2H2(g) + 4OH-(aq) → 4e- + 4H2O(1)
- Net reaction: 2H2 + O2 → 2H₂O
- Fuel cells are very efficient and have very low emissions
Corrosion and Its Prevention
- Iron is one of the metals most commonly affected by corrosion.
- Rust is hydrated iron(III) oxide
- 4Fe(s) + 3O2(g) + xH2O(1) → 2Fe2O3 •xH2O(S)
- The anode and cathode reactions occur at different regions of the metal surface
- Anode reaction: Fe(s) → Fe2+(aq) + 2e-
- Cathode reaction: O2(g) + 2H2O() + 4e- → 4OH-(aq)
- For corrosion to occur, water and oxygen has to be present with the iron
Galvanizing
- Coating steel with zinc in a process called galvanizing can prevent corrosion
- Zinc is more easily oxidized than iron
- Zinc will react before the iron is oxidized; this is called cathodic protection
- The more easily oxidized metal used is called a sacrificial anode
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