What is the Difference between electrochemical equivalent and chemical equivalent?

Answer 1

Electrochemical equivalent is one mole of ionized substance divided by its valency.It is concerned with ions.

chemical equivalent is the weight of a substance that is chemically equivalent to 8.000g of oxygen

Answer 2

To understand electrical and chemical gradients from a physiological perspective it is important to first understand that (1) a cell membrane consists of lipid molecules that are non-conducting and act as an impermeable barrier to ionic species such as Na+ and K+, among others. (2) Permeability to ionic species is a result of channels that span the cell membrane allowing one or more ionic species to diffuse across the cell membrane. Thus the cell membrane is partially permeable and the relative permeabilities for the different ionic species are different. (3) During homeostatic equilibrium there is a difference in the bulk concentration of certain ionic species between the intracellular and extracellular regions. The most important of these species are: Na+, K+, Ca2+, and Cl-. The differences in bulk concentrations on either side of the cell membrane are a result of physiological processes. The consequences of the above statements are immense.

A difference in the bulk concentration of an ionic species on either side of the membrane sets up a chemical gradientacross the membrane. If the membrane is permeable to that species, there will be a movement of ions down the concentration gradient. That is, from the side with higher concentration of the ion to the side with the lower concentration. For example, Na+ exists in greater concentration in the extracellular space than in the intracellular space. Therefore channels allowing the passive movement of Na+ ions will favour the transport of Na+ ions from the extracellular space to the intracellular space. Movement of an ionic species up it's concentration gradient requires the supply of energy for transport. In the above case, energy has to be expended to move Na+ from the intracellular space to the extracellular space. During homeostatic equilibrium, the net flow of ions across the membrane is zero, although there will be movement of ions from either side. To continue with the example of Na+, during homeostatic equilibrium Na+ ions will go from the intracellular to the extracellular space and vice-versa, except that on average as many will cross over from one side as to the other. There will be no change in the bulk concentrations of Na+ ion unless the equilibrium is disturbed.

The fundamental equation that describes the amount of work dWc required to transport a small number of moles of ions dn of an ionic species X which exists in concentration [X]e extracelllularly and [X]i intracellularly (with [X]e > [X]i, i.e., up the concentration gradient) is given by thermodynamics.

dWc = dn RT loge([X]e/[X]i), ... (1)

where R is the gas constant (8.314 J deg-1mole-1), T is the absolute temperature. Strictly speaking we should be using activities of X instead of concentrations, but assuming that the activity coefficient is the same on both sides, Eq. (1) is valid.

As a small number of ions move across the cell membrane, carrying either a negative or positive charge, a potential difference is setup across the membrane. That is, the membrane becomes polarized. This imbalance causes an electrical gradient to be setup across the cell membrane with a tendency to move ions down the gradient. for example, if Na+ ions were to move from the extracellular space to the intracellular space downtheir chemical gradient, then there will be a net buildup of positive charge inside the cell which causes a flow of Na+ ions from the intracellular space to the extracellular space downthe electrical gradient. (In a cell the charge imbalance occurs only in the immediate region of the cell membrane).

The amount of work dWe required to transport a small number of moles of ions dn against the electrical gradient is given by:

dWe = dn zFE, ... (2)

where z is the charge on the ion, F is Faraday's constant (96500 coulombs mole-1) and E is the potential difference across the membrane (measured as the potential of the intracellular side with respect to the extracellular side, Vi - Ve).

Note above that the flow of ions occurs in opposite directions for the two types of gradients. As the potential builds up across the cell membrane due to the movement of ions it becomes harder for the chemical gradient to work against the electrical gradient (or equivalently for the electrical gradient to work against the chemical gradient). During equilibrium (or homeostatsis) the electrical gradient for an ionic species just balances the chemical gradient for that species.

Within a cell only a small number of ions are moved across the membrane, and the bulk concentrations are hardly changed. Therefore from Eqs. (1) and (2) we can calculate the equilibrium condition where there is no net movement of the ionic species X across the cell membrane. This is obtained by setting the two equations to be equal.

dWc = dWe,

i.e., dn RT loge([X]i/[X]e) = dn zFE,

i.e., E = RT/zF loge([X]i/[X]e). ... (3)

Equation (3) is known as the Nernst equation. It specifies the equilbrium potential for one ionic species. When more ionic species are present and to which the cell membrane is permeable, the "resting" membane potential has contributions from several ionic species. In this case the Nernst equation is replaced with a modified equation known as the Goldman-Hodgkin-Katzequation.

Answer 3

Chemical Reaction : - In the chemical reaction, electrons are transferred from one species to another directly in the same medium.

Electrochemical reactions : - In these reactions, the electrons are transferred from one species to another indirectly through the electrodes placed in the same or different medium.

Answer 4

Chemical corrosion

electro chemical corrosion

Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen.

Corrosion in an aqueous environment and in an atmospheric environment (which also involves thin aqueous layers) is an electrochemical process because corrosion involves the transfer of electrons between a metal surface and an aqueous electrolyte solution

In other words, corrosion is the wearing away of metals due to a chemical reaction.

Many structural alloys corrode merely from exposure to moisture in the air, but the process can be strongly affected by exposure to certain substances (see below). Corrosion can be concentrated locally to form a pit or crack, or it can extend across a wide area more or less uniformly corroding the surface. Because corrosion is a diffusion controlled process, it occurs on exposed surfaces. As a result, methods to reduce the activity of the exposed surface, such as passivation and chromate-conversion, can increase a material's corrosion resistance. However, some corrosion mechanisms are less visible and less predictable.

Electrochemical corrosion occurring under such conditions is a major destructive process that results in such costly, unsightly, and destructive effects as the formation of rust and other corrosion products, the creation of the gaping holes or cracks in aircraft, automobiles, boats, gutters, screens, Plumbing, and many other items constructed of every metal except gold.

Answer 5

Chemical Reaction : - In the chemical reaction, electrons are transferred from one species to another directly in the same medium.

Electrochemical reactions : - In these reactions, the electrons are transferred from one species to another indirectly through the electrodes placed in the same or different medium.

What_is_the_difference_between_a_chemical_reaction_and_an_electrochemical_reaction

Answer 6

The mass of an element liberated per unit quantity of electricity passed through an electrolyte in an electrochemical reaction is known as electrochemical equivalent. Whereas, the ratio of atomic weight to valency of an element is known as chemical equivalent of the element.

Answer 7

The electrochemical equivalent is the mass of a substance transformed per unit of electric charge passed during an electrolysis process, while the chemical equivalent is the mass of a substance that reacts or combines with a fixed amount of another substance in a chemical reaction. The electrochemical equivalent is specific to electrolysis, whereas the chemical equivalent is more broadly used in stoichiometry.