equilibrium

1. A condition in which all acting influences are canceled by others, resulting in a stable, balanced, or unchanging system.
2. Mental or emotional balance; poise.
3. Physics. The state of a body or physical system at rest or in unaccelerated motion in which the resultant of all forces acting on it is zero and the sum of all torques about any axis is zero.
4. Chemistry. The state of a chemical reaction in which its forward and reverse reactions occur at equal rates so that the concentration of the reactants and products does not change with time.

[Latin aequilībrium : aequi-, equi- + lībra, balance.]

A stochastic process is said to be in equilibrium if, for every state of the process and for each time point, the probability of being in that state at the next time point is equal to the probability for the current time point.

A state in which a system has its energy distributed in the statistically most probable manner; a state of a system in which forces, influences, reactions, etc., balance each other out so that there is no net change. A body is said to be in thermal equilibrium if no net heat exchange is taking place within it or between it and its surroundings. A system is in chemical equilibrium when a reaction and its reverse are proceeding at equal rates (see also equilibrium constant). These are examples of dynamic equilibrium, in which activity in one sense or direction is in aggregate balanced by comparable reverse activity.

For more information on equilibrium, visit Britannica.com.

The state in which market supply and demand balance each other and, as a result, prices become stable.

Investopedia Says:
The equilibrium price is the price at which the supply of goods matches demand.

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Status of a market in which there are no forces operating that would automatically set in motion changes in the quantity demanded or the price that currently prevails.

noun

A stable state characterized by the cancellation of all forces by equal opposing forces: balance, counterpoise, equipoise, stasis. See order/disorder.

Definition: balance; evenness
Antonyms: imbalance, unevenness

The state of being equally balanced; a state of a body in which the forces acting on it are equally balanced.

According to occultist Éliphas Lévi, magic harmony is said to depend upon equilibrium. In ceremonial magic operations, if the will of the operator is always at the same tension and directed along the same line, moral impotence will ensue. On the other hand, mediums who submit themselves passively to psychic forces are equally unbalanced. Lévi extols the all-powerful action of harmony in exalting the soul and giving it rule over the senses, guided by the will.

Sources:

Lévi, Éliphas. Transcendental Magic. New York: Samuel Weiser, 1972.

In economics, a state of the economy in which for every commodity or service (including labor), total supply and demand are exactly equal. Equilibrium is never actually attained; it is approximated by movements of the market.

A condition in which all influences acting cancel each other, so that a static or balanced situation results. In physics, equilibrium results from the cancellation of forces acting on an object. In chemistry, it occurs when chemical reactions are proceeding in such a way that the amount of each substance in a system remains the same. (See chemical equilibrium.)

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A system in dynamic equilibrium is a particular example of a system in a steady state. In a steady state the rate of inputs is equal to the rate of outputs so that the composition of the system is unchanging in time. For example, a lake is in a steady state when water flows in at the same rate as water flows out.

The very specialized term 'thermodynamic equilibrium' is used in thermodynamics for an isolated system in which the rate of every internal forward reaction is equal to the rate of its backward reaction, and there is no actual transport of matter or energy. This is the principle of detailed balance. Both reactions do in fact occur, sometimes vigorously, but to such a closely balanced extent that changes in composition cannot be observed.

For example, in a new bottle of cola the concentration of carbon dioxide in the liquid phase has a particular value. If half the liquid is poured out and the bottle is sealed, carbon dioxide will leave the liquid phase at an ever decreasing rate and the partial pressure of carbon dioxide in the gas phase will increase until equilibrium is reached. At that point a molecule of CO₂ may leave the liquid phase, but then another molecule of CO₂ will pass from the gas to the liquid. At equilibrium the rate of loss of CO₂ is equal to the rate of gain. In this case, the equilibrium concentration of CO₂ in the liquid is given by Henry's law, which states that the solubility of a gas in a liquid is directly proportional to the partial pressure of that gas above the liquid. This relationship is written as

where k is a temperature-dependent constant, p is the partial pressure and c is the concentration of the dissolved gas in the liquid. Thus, the partial pressure of CO₂ in the gas has increased until Henry's law is obeyed. The concentration of carbon dioxide in the liquid has decreased and the drink has lost some of its fizz.

Henry's law may be derived by setting the chemical potentials of carbon dioxide in the two phases to be equal to each other. Equality of chemical potential defines chemical equilibrium. Other constants for dynamic equilibrium involving phase changes include partition coefficient and solubility product. Raoult's law defines the equilibrium vapor pressure of an ideal solution.

Dynamic equilibria can also exist in a homogeneous system. A simple example occurs with acid-base equilibria such as the "dissociation" of acetic acid, in aqueous solution.

CH₃CO₂H CH₃CO₂^- + H⁺

At equilibrium the concentration quotient, K, the acid dissociation constant, is constant (subject to some conditions)

In this case, the forward reaction involves the liberation of some protons from acetic acid molecules and the backward reaction involves the formation of acetic acid molecules when an acetate ion accepts a proton. Equilibrium is attained when the sum of chemical potentials of the species on the left-hand side of the equilibrium expression is equal to the sum of chemical potentials of the species on the right-hand side. At the same time the rates of forward and backward reactions are equal to each other. Equilibria involving the formation of chemical complexes are also dynamic equilibria and concentrations are governed by the stability constants of complexes.

Dynamic equilibria can also occur in the gas phase as, for example, when nitrogen dioxide dimerizes.

2NO₂ N₂O₄;

It should be noted that in the gas phase, square brackets are not used as these indicate a concentration, instead a capitalised P is used to indicate partial pressure.

See also

• Static equilibrium
• Chemical equilibrium
• Radiative equilibrium

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Common misspelling(s) of equilibrium

• equilibrum
• equilibium

Dansk (Danish)
n. - balance, ligevægt, sindsro, balancetilstand

Nederlands (Dutch)
evenwicht, evenwichtigheid

Français (French)
n. - équilibre, aplomb, stabilité

Deutsch (German)
n. - Gleichgewicht

Ελληνική (Greek)
n. - ισορροπία

Italiano (Italian)
equilibrio

Português (Portuguese)
n. - equilíbrio (m)

Русский (Russian)
равновесие, уравновешенность, самообладание

Español (Spanish)
n. - balance, equilibrio

Svenska (Swedish)
n. - jämvikt, jämviktsläge, avvägande

中文（简体）(Chinese (Simplified))
平衡, 均衡, 平静

中文（繁體）(Chinese (Traditional))
n. - 平衡, 均衡, 平靜

한국어 (Korean)
n. - 균형, 평온

日本語 (Japanese)
n. - 釣合い, 平衡, 安定

العربيه (Arabic)
‏(الاسم) توازن‏

עברית (Hebrew)
n. - ‮שיווי משקל, איזון נפשי או שכלי‬

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