Questions and Answers
What flows in metallic conduction?
Which of the following laws are followed in electrolytic conduction?
What is the primary role of electrolytes in a solution?
How does the resistance of electronic conductors change with temperature?
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What happens at the zinc electrode in a Daniel cell?
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What is a key feature of galvanic cells?
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Which type of conductors experience a decrease in resistance with temperature?
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What distinguishes electrolytic conduction from metallic conduction?
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What role does the Zn electrode play in an electrochemical cell?
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Which equation correctly represents the oxidation half-reaction at the Zn rod?
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What is the function of the salt bridge in an electrochemical cell?
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At the copper electrode, what type of reaction occurs?
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Study Notes
Electrochemistry Overview
- Electrochemistry involves generating electrical energy from spontaneous chemical reactions and using electrical energy to drive non-spontaneous reactions.
Conductors
- Conductors enable electric current flow and are categorized as metallic or electrolytic.
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Metallic Conductors:
- Current flows via electron movement, without chemical change or matter transfer.
- Resistance increases with temperature.
- Examples include metals, certain alloys, and non-metals like graphite.
Electrolytic Conduction
- Electrolytes are substances that, when dissolved in water, allow current to pass and undergo chemical decomposition.
- Current flows through the movement of ions, involving transfer of matter as ions.
- Ohm's Law and Faraday's Laws of Electrolysis are applicable.
- Resistance decreases with an increase in temperature.
Galvanic (Voltaic) Cells
- Galvanic cells convert chemical energy into electrical energy.
- Composed of two half cells connected by a salt bridge to prevent mixing of solutions.
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Example: Daniel Cell:
- One half cell contains a zinc rod in zinc sulfate solution; the other contains a copper rod in copper(II) sulfate solution.
- Zinc electrode undergoes oxidation, converting Zn to Zn²⁺ ions in solution.
Anode and Cathode
- The Zn electrode serves as the anode, where it accumulates electrons and becomes negatively charged.
- Electrons released from the Zn rod travel through the circuit to the Cu electrode.
- The Cu electrode acts as the cathode, which is positively charged, where reduction occurs.
- The oxidation half-reaction at the Zn rod:
Zn(s) → Zn2+(aq) + 2e - The reduction half-reaction at the Cu electrode:
Cu2+(aq) + 2e → Cu(s) - The overall net redox reaction combines both half-reactions:
Zn(s) + Cu2+(aq) → Cu(s) + Zn2+(aq)
Salt Bridge and its Significance
- The salt bridge consists of an inverted U-tube filled with concentrated solutions of inert electrolytes (e.g., KCl, KNO3, NH4NO3).
- Ends of the salt bridge are plugged with cotton wool to reduce diffusion effects.
- Inert electrolytes in the salt bridge do not undergo electrochemical reactions.
- The salt bridge maintains electrical neutrality by allowing ions to move between the half cells filled with agar-agar gel or gelatin.
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Description
This quiz dives into the fundamentals of electrochemistry, focusing on the interplay between chemical reactions and electrical energy. It highlights the characteristics of conductors and differentiates between metallic and electrolytic conduction.
