Electrochemistry Overview and Half-Cell Reactions

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Questions and Answers

Which substance is likely to be reduced first when the potential of an electrode is moved to more negative potentials?

The oxidant with the most negative reduction potential

The oxidant with the highest reduction potential

The oxidant with the least positive reduction potential

The oxidant with the least negative reduction potential (correct)

What does current density depend on when discussing over-potential?

All types of overpotential combined (correct)

Only charge-transfer overpotential

Only mass-transfer overpotential

Only overpotential associated with preceding reactions

In the context of electrocatalysis, what is meant by the 'power of electrode surface'?

The conductivity of the electrode material

The ability of the electrode to facilitate reactions (correct)

The surface area of the electrode only

The temperature of the electrode surface

What does the symbol 'O' represent in the general electrode reaction O + ne ↔ R?

The oxidant in the reaction Signup and view all the answers

Which of the following statements about charge-transfer overpotential is correct?

It can influence the rate of the overall electrochemical reaction. Signup and view all the answers

What is the relationship between the potential of the Pt electrode and the onset of current flow?

Current flow begins when the Pt potential is equal to 0 V vs.NHE. Signup and view all the answers

In comparison to Pt, what characteristic does the mercury electrode exhibit regarding hydrogen evolution reaction?

It requires more negative potentials to initiate the reaction. Signup and view all the answers

What occurs if the potential of the Pt electrode is made more negative with respect to the Ag/AgBr reference electrode?

Electrons flow from the electrode to protons in solution. Signup and view all the answers

What does the conventional notation denote regarding cathodic current?

Cathodic current is denoted as negative. Signup and view all the answers

What is the significance of E° for the H+/H2 reaction in this context?

It serves as the reference point for determining when current will flow. Signup and view all the answers

How is the potential axis converted to EPt (V vs.NHE)?

By adding 0.07 V to each potential value. Signup and view all the answers

What phenomenon occurs in a cell when no equilibrium can be achieved in one of the half cells?

A continuous reaction will be observed without stabilizing. Signup and view all the answers

Which statement best describes overpotential in the context of the mercury electrode?

The mercury electrode exhibits higher overpotential due to slower reaction rates. Signup and view all the answers

Study Notes

Recap of Electrochemistry

Examples of half-cell and full-cell reactions are included.
Cell voltage and potential vs. reference are discussed.
Examples of galvanic and electrolytic cell operation, based on prior concepts, are provided.
Examples of cells where equilibrium cannot be achieved in one of the half-cells are shown.

Half-Cell Reactions and Oxidation/Reduction Currents

Half-cell reactions are defined and include oxidation/reduction processes.
A diagram illustrating a power supply connected to electrochemical cells is presented.
The potential of a platinum electrode, related to hydrogen/hydrogen ions, is explained, along with cathodic and anodic current.
Equations for half-cell reactions, including those for silver bromide, are given.

Half-Cell Reactions - Overpotential

The same electrochemical cell with a mercury electrode instead of platinum is examined within a diagram.
Comparing the cell with a platinum electrode, a diagram is included illustrating the current as a function of potential vs. NHE.
Cases for cells without current under specific potential ranges are observed.

Adding Other Cations/Species to Electrolyte

Adding other cations or species to the electrolyte affects the reduced substances' order of priority.
The oxidant with the least negative reduction potential is reduced first.
An equation related to the reaction when cadmium ions are added is included.
Diagram explaining reduction/oxidation behavior when other species are introduced is given.

Rate and Pathway of Electrode Reaction

The rate of a general electrode reaction with respect to time is described.
The equation for current and how it relates to the number of moles electrolyzed is presented, along with defining terms for surface region and bulk solution for electrochemical reactions.
The different types of over-potentials that affect the rate and pathways observed in electrochemical reactions are differentiated.

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Description

This quiz covers key concepts in electrochemistry, focusing on half-cell and full-cell reactions. It explores cell voltage, the operation of galvanic and electrolytic cells, and details oxidation and reduction processes in half-cells. Diagrams and equations are included to reinforce learning through visual representation.