Question

Define electrochemical equivalent.

Short answer

Answer: The electrochemical equivalent (Z or E.C.E) is the mass of a substance deposited or liberated at an electrode during an electrochemical reaction per unit charge (1 Coulomb). It can be calculated using the formula: \[Z = \frac{M}{n × F}\] Where M is the molar mass of the substance (in grams/mol), n is the valency of the substance (number of electrons involved in the reaction), and F is the Faraday's constant (approx. 96485 C/mol). The unit of measurement for electrochemical equivalent is grams per Coulomb (g/C). This concept is useful for determining the efficiency of an electrochemical reaction and designing electrochemical processes like electrolysis and electrosynthesis.

Step-by-step solution

Definition of Electrochemical Equivalent

The electrochemical equivalent, often denoted as "Z" or "E.C.E", is a measure of the mass of a substance deposited or liberated at an electrode during an electrochemical reaction. It is defined as the mass of a substance deposited or liberated per unit charge (i.e., 1 Coulomb of charge) passed during the electrochemical process. In simpler terms, it tells us how much mass of a substance is deposited or liberated when a certain amount of charge is passed through an electrochemical cell.

Relation with atomic weight, valency, and Faraday's constant

The electrochemical equivalent can be found by dividing the molecular weight (in grams) of the substance by its valency and the Faraday's constant (approximately 96485 C/mol). Mathematically, it can be expressed as: \[Z = \frac{M}{n × F}\] Where: - Z is the electrochemical equivalent, - M is the molar mass of the substance (in grams/mol), - n is the valency of the substance (number of electrons involved in the reaction), and - F is the Faraday's constant (approx. 96485 C/mol).

Units and significance

The unit of measurement for electrochemical equivalent is grams per Coulomb (g/C). It is an important concept, as it helps in determining the efficiency of an electrochemical reaction, as well as designing electrochemical processes like electrolysis and electrosynthesis. By knowing the electrochemical equivalent of a substance, we can predict the amount of material deposited or liberated at the electrodes, enabling us to optimize and control electrochemical processes.

Key concepts

Electrochemistry

Electrochemistry is a branch of chemistry that deals with the relationship between electrical energy and chemical reactions. When an electric current is passed through a solution or a molten substance, it can cause chemical changes — a process known as electrolysis. In this process, atoms and molecules undergo oxidation-reduction (redox) reactions at the electrodes. The cathode attracts cations (positive ions), where reduction occurs (gain of electrons), and the anode attracts anions (negative ions), where oxidation happens (loss of electrons).

Understanding electrochemistry is fundamental for various applications such as batteries, fuel cells, and electroplating. For instance, in electroplating, a metal (like silver or nickel) is deposited onto another material to enhance durability, corrosion resistance, or appearance. The principles of electrochemistry also help us quantify and predict the outcomes of these redox reactions.

Faraday's Constant

Faraday's constant, denoted by the symbol F, represents the total charge carried by one mole of electrons. Its approximate value is 96,485 Coulombs per mole (C/mol). This constant is named after the eminent scientist Michael Faraday, who made significant contributions to the field of electrochemistry.

The significance of Faraday's constant lies in its use for calculating the charge required to deposit or dissolve a mole of substance during electrochemical reactions. It is a bridge between the macroscopic world we can measure (like moles of a chemical substance) and the microscopic world of electric charges carried by electrons. It is crucial in applying the laws of electrolysis, and in the determination of the electrochemical equivalent of any material.

Molar mass

Molar mass is a physical property defined as the mass of a given substance (chemical element or chemical compound) divided by the amount of substance. The molar mass is typically expressed in units of grams per mole (g/mol) and can be calculated by summing the atomic masses of the constituent atoms in a single molecule of a substance. When dealing with electrochemistry, the molar mass becomes essential for calculating the electrochemical equivalent as it denotes how heavy one mole of a substance is, which, in turn, relates to how much mass is expected to be deposited during an electrochemical reaction.

Valency

Valency is the measure of an element's combining power with other atoms when it forms chemical compounds or molecules. In the context of electrochemistry, valency refers to the number of electrons an atom can lose, gain, or share during a chemical reaction. It becomes crucial in understanding the stoichiometry of an electrochemical reaction which dictates how many electrons are involved in the oxidation or reduction processes occurring at the electrodes.

A higher valency means more electrons are transferred during the reaction, affecting the mass of a substance that will be deposited or liberated. Thus, understanding valency is integral when calculating the electrochemical equivalent since it directly influences the equation \(Z = \frac{M}{n \times F}\) with 'n' representing the valency of the substance involved.