Standard Electrode Potential

The amount of a cell’s standard emf is known as Standard Electrode Potential. Under standard pressure, the cell’s molecular hydrogen is oxidized to form solvated protons. An electromotive force called electrode potential exists between two electrodes in a cell. It is impossible to determine an electrode’s precise value. So one can measure the difference between the electrodes by experimentation.

Standard electrode potential

                                                                                    Standard electrode potential

Definition of Standard Electrode Potential

Half-cell or half-reaction potential is the potential of the half-reaction (half cell) measured against a standard hydrogen electrode in a given set of conditions. Standard conditions call for a 298K temperature, a 1 atm pressure, and a 1M electrolyte concentration. With reference to typical hydrogen electrodes, it is measured.

Significance of Standard Electrode Potential

Redox reactions occur in two of the half-reactions that make up an electrochemical cell. Oxidation occurs at the anode end while reduction occurs at the cathode end. Electrons are lost at the anode end and gained at the cathode end as a result of oxidations. Electricity is thus conducted as a result of the movement of electrons from anode to cathode. When an electrode is submerged in its electrolyte, the potential difference between the cathode and anode creates an electric potential. A voltmeter is used to measure this cell potential. Standard reduction potentials for good oxidising agents are high, while standard reduction potentials for good reducing agents are low.

Standard Electrode Potential Example

The calculation of a zinc electrode’s standard electrode potential in relation to a standard hydrogen electrode is shown in the picture below (SHE). Potential is measured under typical conditions, which include 298K temperature, 1 atm pressure, and 1M electrolyte concentration.

The Spontaneity of Redox Reactions

A redox reaction must be spontaneous for the Gibbs free energy to be negative. The following equation provides an explanation:

ΔGocell = -nFE0cell

For every mole of product created, there are n moles of electrons in total, and F stands for Faraday’s constant (approximately 96485 C.mol-1).

Importance of a Standard Electrode Potential

The foundation of any electrochemical cell is the redox process, which consists of two parts. The anode is where the oxidation half-reaction takes place, resulting in electron loss. An electron gain results from a reduction process that takes place at the cathode. Electrons flow from the anode to the cathode as a result.

The electric potential between the anode and the cathode is brought about by the variation in the individual potentials of each electrode. As a reference electrode, it is measured using a standard hydrogen electrode (SHE). The electrode potential of SHE is zero volts. When an electrode is connected to the SHE, the cell potential of the resulting galvanic cell can be used to calculate the electrode’s standard electrode potential.

Uses of Standard Electrode Potential

  • We are able to determine the relative potency of a variety of oxidants, reactants, and other substances.
  • It is possible to determine the Standard Cell Potential Value for a number of different chemical species.
  • We are able to determine in advance whether or not specific chemical species will react with one another and, if so, to what extent that reaction will be.
  • When trying to forecast where the point of equilibrium will be in a chemical reaction, the standard electrode potential is a useful tool.

Limitation of Standard Electrode Potential

Only the equilibrium of aqueous solutions may be measured using standard electrode potentials. Using typical electrode potentials, we are able to forecast the reaction possibilities, but we are unable to estimate the rate at which the reaction would occur.

FAQs on Standard Electrode Potential

Question 1. What exactly is a reversible electrode?

Answer. A reversible electrode has a potential that is determined by changes that can be reversed. One of the fundamental conditions is that the system is near chemical equilibrium. The system must also be subjected to extremely small stimuli over a sufficiently long period of time that chemical equilibrium conditions almost invariably prevail.

Reversible conditions are difficult to achieve experimentally because each perturbation applied to a system nearing equilibrium in a finite time forces it out of equilibrium. However, an electrode is considered reversible provided the stimuli made to the system are small and supplied slowly enough. The reversibility of an electrode is essentially reliant on the experimental settings and the method in which it is utilized.

Question 2. What is the standard electrode potential’s dissolving potential?

Answer. Standard electrode potentials recorded with respect to hydrogen are of theoretical importance. They only apply to pure metals, not alloys, and they do not take into consideration possible passivation processes, as illustrated by aluminium. They are measured in an unusual medium: a standard solution of the salt of the metal under concern. Corrosion experts, on the other hand, prefer dissolving potentials, which are measured with respect to an easy-to-use reference electrode and the medium of their choice, such as real saltwater or a standard liquid.

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