Sel Elektrokimia (2) | Sel Volta (Sel Galvani | Kimia Kelas 12

Summary

In this educational video, viewers learn about Voltaic Cells (also known as Galvani cells), which convert chemical energy from spontaneous redox reactions into electrical energy. The video covers key concepts like reduction potential, how to identify the anode and cathode, and how to calculate cell potential (E°cell). Through an example involving silver (Ag) and copper (Cu), the video demonstrates how to determine cell reactions, notations, and electron flow. The content is aimed at helping students understand the principles of electrochemistry in a practical and engaging way.

Takeaways

• 😀 Voltaic cells convert chemical energy from spontaneous redox reactions into electrical energy or current.
• 😀 Reduction potential (E°) indicates how easily a substance gains electrons; a higher E° means it is more likely to be reduced.
• 😀 Standard reduction potential is measured under standard conditions: 25°C, 1 M concentration, and 1 atm pressure.
• 😀 The electrode with the higher reduction potential acts as the cathode (positive electrode), while the lower reduction potential acts as the anode (negative electrode).
• 😀 To calculate the cell potential (E°cell), subtract the anode's E° from the cathode's E°: E°cell = E°cathode - E°anode.
• 😀 A positive E°cell indicates a spontaneous redox reaction.
• 😀 In voltaic cells, reduction reactions occur at the cathode, where electrons are gained, while oxidation occurs at the anode, where electrons are lost.
• 😀 The overall cell reaction is obtained by adding the half-reactions from the anode (oxidation) and cathode (reduction).
• 😀 Cell notation follows the format: anode | anode ions || cathode ions | cathode, separated by a salt bridge.
• 😀 Electron flow in a voltaic cell is from the anode (negative) to the cathode (positive) in the external circuit.
• 😀 Example: For silver (Ag) and copper (Cu), Ag has a higher reduction potential, so it becomes the cathode, and Cu becomes the anode. The cell potential for this reaction is 0.46 V.

Q & A

What is a voltaic cell?

A voltaic cell, also known as a Galvanic cell, is an electrochemical cell that converts the energy from spontaneous redox reactions into electrical energy or electric current.

What is reduction potential in the context of voltaic cells?

Reduction potential (E°) is the tendency of a substance to gain electrons and undergo reduction. It is measured under standard conditions at 25°C, with 1 molar concentration of ions and 1 ATM pressure.

How is the reduction potential of a substance related to its tendency to undergo reduction or oxidation?

A more positive reduction potential indicates that a substance is more likely to undergo reduction. Conversely, a more negative reduction potential suggests it is less likely to be reduced and more likely to undergo oxidation.

How do you determine which electrode is the anode and which is the cathode in a voltaic cell?

The cathode is the electrode where reduction occurs, and it has the higher reduction potential. The anode is where oxidation occurs and has the lower reduction potential.

How is the cell potential (E°cell) calculated?

The cell potential is calculated by subtracting the reduction potential of the anode (oxidation site) from that of the cathode (reduction site). The result should be positive for a spontaneous reaction.

What is the notation for a voltaic cell?

The notation for a voltaic cell consists of the anode half-reaction on the left, followed by a salt bridge, then the cathode half-reaction on the right. For example: Anode | Anode ions || Cathode ions | Cathode.

What is the direction of electron flow in a voltaic cell?

Electrons flow from the anode (negative electrode) to the cathode (positive electrode) in a voltaic cell.

How do you write the half-reactions in a voltaic cell?

The half-reaction at the cathode involves reduction (gain of electrons), and the half-reaction at the anode involves oxidation (loss of electrons). Both reactions are written with their respective reduction potentials.

What happens if the electrons in a voltaic cell are not balanced?

If the electrons are not balanced, the reactions will not be properly balanced. To correct this, you must multiply the coefficients of the half-reactions by appropriate factors to equalize the number of electrons lost in oxidation and gained in reduction.

Can you give an example of a voltaic cell calculation using silver (Ag) and copper (Cu)?

In an example where silver (Ag) has a reduction potential of +0.80 V and copper (Cu) has a reduction potential of +0.34 V, the silver electrode would be the cathode (reduction site), and copper would be the anode (oxidation site). The cell potential would be 0.80 V - 0.34 V = 0.46 V, indicating a spontaneous reaction.