QUIMICA REDOX T4.7 Potencial estándar de reducción de las semireacciones

Summary

This video script explains the use of the hydrogen electrode as a reference point for comparing the reduction potential of various half-reactions. It outlines the concept of oxidation and reduction potentials, where positive values indicate reduction and negative values indicate oxidation. The script also describes how different elements and compounds are ranked based on their ability to oxidize or reduce, with the most oxidizing substances at the top of the table. Furthermore, the script details how to calculate the standard potential of a galvanic cell by subtracting the anode potential from the cathode potential, providing an example with dichromate and iron.

Takeaways

• 😀 The hydrogen electrode is used to compare the oxidizing and reducing abilities of different half-reactions.
• 😀 The hydrogen electrode is assigned a potential of 0V to allow the comparison of various half-reactions' potentials.
• 😀 Reactions with positive potential values are reduction reactions, while those with negative values represent oxidation reactions.
• 😀 Negative potentials indicate oxidation reactions, meaning the substance loses electrons. Examples include aluminum and zinc.
• 😀 Positive potentials indicate reduction reactions, where the substance gains electrons, such as with chlorine and permanganate.
• 😀 When constructing a galvanic cell, the half-reaction with the higher potential acts as the cathode (reduction) and the lower potential as the anode (oxidation).
• 😀 The more positive the reduction potential, the more oxidizing the substance is. For example, permanganate is more oxidizing than chlorine.
• 😀 The more negative the reduction potential, the more reducing the substance is. For example, aluminum is the most reducing element.
• 😀 When forming a cell, to calculate the cell potential, subtract the anode's potential from the cathode's potential.
• 😀 For example, a cell formed from dichromate and iron has a standard potential of 1.77V, based on the difference between their half-reaction potentials.

Q & A

What is the purpose of the hydrogen electrode in electrochemical reactions?

The hydrogen electrode is used as a reference electrode to compare different half-reactions, determining their oxidizing or reducing abilities.

What does the value of 0V assigned to the hydrogen electrode represent?

The value of 0V is arbitrarily assigned to the hydrogen electrode, allowing for the comparison of potential differences between other half-reactions and the hydrogen electrode.

What does a negative potential value signify when comparing half-reactions to the hydrogen electrode?

A negative potential indicates that the half-reaction is undergoing oxidation, meaning the substance is losing electrons.

What does a positive potential value indicate when comparing half-reactions to the hydrogen electrode?

A positive potential indicates that the half-reaction is undergoing reduction, meaning the substance is gaining electrons.

How can you identify which electrode will act as the anode or cathode in a reaction?

The electrode with a more negative potential will act as the anode (oxidation occurs), while the electrode with a more positive potential will act as the cathode (reduction occurs).

What happens when a half-reaction with a negative potential is connected to the hydrogen electrode?

When a half-reaction with a negative potential is connected to the hydrogen electrode, the oxidation process occurs, meaning the substance will lose electrons and act as the anode.

What does the ordering of half-reactions in a reduction potential table tell us?

The ordering indicates the relative oxidizing or reducing strength of substances. Higher (more positive) potentials indicate stronger oxidizers, while lower (more negative) potentials indicate stronger reducers.

What does it mean when a half-reaction is at the top of the reduction potential table?

A half-reaction at the top of the table has the highest potential for reduction, making it the most oxidizing substance.

How is the standard cell potential for a voltaic cell calculated?

The standard cell potential is calculated by subtracting the standard potential of the anode from that of the cathode.

In a voltaic cell, what is the role of the half-reaction with the more positive potential?

The half-reaction with the more positive potential will undergo reduction and act as the cathode, where electrons are gained.