Name: gas equilibrium under volume changes
Uploaded: 2020-09-24T15:06:51.000Z
Duration: 2 min 32 s
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Chemistry

Matter and its Interactions

PS.Chm.5.2

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Le Chatelier's Principle: Changing Volume (Pressure)

Le Châtelier prensibi, denge durumundaki bir sistemin hacim veya basınçtaki bir değişikliğin stresine nasıl tepki vereceğini tahmin etmek için kullanılabilir. Bir gazın hacmi basıncıyla ters orantılıdır;bu nedenle, dengede olan bir sistem için, hacimdeki azalma, basıncı artırır ve dengeyi bozar. Sonuç olarak, denge pozisyonu stresi en aza indirmek için bir yöne kayacaktır.İdeal gaz yasası, bir gazın basıncının, mol sayısı ile doğru orantılı olduğunu belirtir. Bu nedenle, dengeyi yeniden sağlamak için kayılması gereken yön, reaksiyonun her iki tarafındaki gaz partiküllerinin mol sayısına bağlıdır. Daha fazla gaz molü daha yüksek bir basınçla sonuçlandığından, basınçtaki bir artış, basıncı düşürmek için denge konumunu daha az mol içeren tarafa kaydırır.Aynı şekilde, basınçtaki bir azalma, denge konumunu daha fazla gaz molü ile yana kaydırır. Bir mol gaz halindeki fosfor pentaklorürün, bir mol fosfor triklorür ve bir mol klor gazına ayrıştığı ve toplam iki mol ürünün olduğu bir kimyasal denge düşünün. Piston aşağı doğru itilirse denge sisteminin hacmi basıncı artırarak azalır.Bu, dengeyi bozar ve Q'nun K'den büyük olmasına neden olur. Bu nedenle, denge konumu, basıncı düşürmek ve dengeyi sağlamak için daha az mol gaz parçacığı ile reaktanlara doğru kayar. Tam tersi olarak da pistonu yukarı çekmek hacmi artırır ve basıncı düşürür.Bu durumda Q, K'dan daha küçük olur. Basıncı yükseltmek için, denge konumu, en çok gaz molüne sahip taraf olan ürünlere doğru kayar ve dengeyi yeniden sağlar. Sabit hacimde bir denge karışımına bir inert gaz ekleyerek basıncın arttırılması, dengeyi etkilemez çünkü gaz halindeki reaktanların ve ürünlerin kısmi basınçları değişmeden kalır.İyot monoklorür üretmek için iyot gazı ile klor gazı arasındaki reaksiyon gibi eşit sayıda gaz halindeki reaktan ve ürün molüne sahip denge sistemleri için, sistemin hacmindeki bir değişikliğin denge üzerinde hiçbir etkisi olmayacaktır.

le chatelier prensibi: hacim (basınç) değiştirme

Gaz fazı dengeleri için, reaksiyona giren maddelerin ve ürünlerin konsantrasyonlarındaki değişiklikler, değişen hacim ve basınçla meydana gelebilir. İdeal bir gazın kısmi basıncı, P, molar konsantrasyonu, M ile orantılıdır.
 
 <img alt=""Eq1"" src=""/files/ftp_upload/11392/11392_Equation 1.png"" style=""text-align: center; height: 70px;"" />
 
 Bu nedenle, herhangi bir reaktan veya ürünün kısmi basınçlarındaki değişiklikler esasen konsantrasyonlardaki değişikliklerdir; bu nedenle, bu değişiklikler denge üzerinde aynı etkileri verir. Reaktanların veya ürünlerin eklenmesi veya çıkarılmasının yanı sıra, gaz fazı dengesindeki türlerin basınçları (konsantrasyonları), sistem tarafından işgal edilen hacmi değiştirerek de değiştirilebilir. Bir gaz fazı dengesinin tüm türleri aynı hacmi işgal ettiğinden, hacimdeki belirli bir değişiklik hem reaktan hem de ürünler için konsantrasyonda aynı değişikliğe neden olacaktır. Varsa, bu tür bir stresin neden olacağı kaymayı ayırt etmek için, reaksiyonun stokiyometrisi dikkate alınmalıdır.
 
 Dengede, N2 (g) + O2 (g) ⇌ 2 NO (g) reaksiyonu, reaksiyon katsayısı tarafından tanımlanır
 
 <img alt=""Eq2"" src=""/files/ftp_upload/11392/11392_Equation 2.png"" style=""text-align: center; height: 70px;"" />
 
 Bu türlerin bir denge karışımının kapladığı hacim 3 kat azalırsa, üç türün kısmi basınçları 3 kat artacaktır:
 
 <img alt=""Eq3"" src=""/files/ftp_upload/11392/11392_Equation 3.png"" style=""text-align: center; height: 70px;"" />
 
 Ve bu nedenle, bu gaz fazı denge karışımının hacmini değiştirmek, dengede bir kaymaya neden olmaz.
 
 Bununla birlikte, farklı bir sisteme benzer bir işlem 2 SO2 (g) + O2 (g) ⇌ 2 SO3 (g), farklı bir sonuç verir:
 
 <img alt=""Eq4"" src=""/files/ftp_upload/11392/11392_Equation 4.png"" style=""text-align: center; height: 200px;"" />
 
 Bu durumda, hacimdeki değişiklik, denge sabitinden daha küçük bir reaksiyon katsayısıyla sonuçlanır ve bu nedenle denge sağa kayar.
 
 Bu sonuçlar, bir gaz fazı dengesinin stokiyometrisi ile hacim kaynaklı basınç (konsantrasyon) değişikliğinin etkisi arasındaki ilişkiyi göstermektedir. İlk örnekte olduğu gibi, reaktanların ve ürünlerin toplam molar miktarları eşitse, hacimdeki bir değişiklik dengeyi değiştirmez. Reaktanların ve ürünlerin molar miktarları farklıysa, hacimdeki bir değişiklik, dengeyi hacim değişikliğine daha iyi “uyum sağlayan” bir yönde kaydıracaktır. İkinci örnekte, üç mol reaktan (SO2 ve O2) iki mol ürün (SO3) verir ve bu nedenle sistem hacminin azaltılması dengenin sağa kaymasına neden olur, çünkü ileri reaksiyon ters reaksiyondan (3 mol) daha az gaz (2 mol) üretir. Tersine, bu denge sisteminin hacmini artırmak, reaktanlara doğru bir kaymaya neden olur.
 
 Bu metin bu kaynaktan uyarlanmıştır: <a href=""https://openstax.org/books/chemistry-2e/pages/13-3-shifting-equilibria-le-chateliers-principle"">Openstax, Chemistry 2e, Section 13.3 Shifting Equilibria: LeChatelier’s Principle</a>.

Le Chatelier Prensibi: Hacim (Basınç) Değiştirme

Gaz fazı dengesi için, reaktanların ve ürünlerin konsantrasyonlarındaki değişiklikler, değişen hacim ve basınçla meydana gelebilir. Kısmi basınç, P, ...

Education

JoVE Core

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Chemical Equilibrium

Kimyasal Denge

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

gas equilibrium under volume changes

Gas-phase equilibrium can shift when the volume of the system changes. In these reactions, a change in pressure changes concentration because the partial pressure of an ideal gas is proportional to its molar concentration. That means pressure changes affect equilibrium in the same way as concentration changes.

When the volume of a gas mixture changes, the concentrations of reactants and products change together. Since every gas in the equilibrium occupies the same space, the same volume change affects each species in the same way. To predict whether the equilibrium shifts, you must look at the reaction stoichiometry.

For the equilibrium N2(g) + O2(g) ⇌ 2 NO(g), decreasing the volume by a factor of 3 increases the partial pressures of all three gases by a factor of 3. In this case, the reaction quotient still matches the equilibrium position, so the equilibrium does not shift. The total moles of reactants and products are equal, and that is why the volume change has no effect.

A different result appears for 2 SO2(g) + O2(g) ⇌ 2 SO3(g). Here, decreasing the volume makes the reaction quotient smaller than the equilibrium constant, so the equilibrium shifts right. Three moles of reactant form two moles of product, so the forward reaction makes less gas. Increasing the volume would shift this system toward the reactants.

Gas Equilibrium Under Volume Changes

the equilibrium constant

Chemical Equilibrium and Kc Rules

Chemical equilibrium and the equilibrium constant Kc describe how reactants and products are balanced in a reaction. In the oxidation of sulfur dioxide, a mixture that starts with reactants only has no product at first. As the reaction moves forward toward equilibrium, reactant concentrations decrease and product concentration increases. When equilibrium is reached, the concentrations of both stay constant. A reaction can also begin with only products present. In that case, the reaction moves...

homogeneous equilibria for gaseous reactions

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Relating Kc and Kp in Gas Equilibria

Gas-phase equilibrium can be written using either concentration or pressure. The equilibrium constant may be shown as Kc, which uses molar concentration, or as Kp, which uses partial pressure of the reactants and products. The link between Kc and Kp comes from the ideal gas equation and the definition of molarity. Molarity is the number of moles divided by volume. In the ideal gas equation, P stands for partial pressure, V for volume, n for number of moles, R for the gas constant, and T for...

le chatelier's principle: changing concentration

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Shifting Equilibrium by Changing Concentration

Chemical equilibrium is a dynamic balance. At equilibrium, the forward and reverse reactions happen at equal rates. If the system is stressed in a way that changes one rate more than the other, it is no longer at equilibrium and will shift until balance is restored. This behavior is described by Le Châtelier’s principle. Changes in concentration are a major stress on an equilibrium system. Reaction rates depend mainly on concentration and temperature. For that reason, changing the amount of a...

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Finding Kc from Equilibrium Data

The equilibrium constant, Kc, can be found from the equilibrium concentrations of reactants and products. When those concentrations are known, the calculation is straightforward. The values are placed into the Kc expression for the reaction. One example uses nitrogen dioxide and dinitrogen tetroxide. When 0.10 mol NO2 is added to a 1.0-L flask at 25 °C, the concentrations change until equilibrium is reached. At equilibrium, [NO2] is 0.016 M and [N2O4] is 0.042 M, and these values are used to...

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Using Q to Track Equilibrium Changes

Reaction quotient Q helps track how far a reversible reaction has moved toward equilibrium. For a balanced reaction such as m A + n B ⇌ x C + y D, Q comes directly from the stoichiometric coefficients in the equation. When concentrations are used, the expression is written as Qc. For gases, a similar form uses partial pressures. These expressions use relative concentration and pressure values, not absolute values. That means reaction quotients are dimensionless and have no units. As a reaction...

dynamic equilibrium

Chemical Equilibrium in Reversible Reactions

Chemical equilibrium in reversible reactions happens when a reaction moves in both directions at the same time. A reversible reaction uses a double arrow to show that products can turn back into reactants. At equilibrium, the concentrations of reactants and products stay constant over time because the forward and reverse reaction rates are equal. The video uses the reversible decomposition of colorless dinitrogen tetroxide to brown nitrogen dioxide as an example. At time zero, there is finite...

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Equilibrium Concentrations from an ICE Table

Equilibrium concentrations can be found from initial concentrations and an equilibrium constant. This skill matters in many areas of science and technology, including pharmaceutical product formulation and dosing. After a drug is ingested or injected, it may take part in several chemical equilibria that change its final concentration in the body system of interest. Scientists use these quantitative equilibrium relationships to help calculate a dosage that will produce the desired therapeutic...

le chatelier's principle: changing volume (pressure)

Gas-phase equilibrium can shift when the volume of the system changes. In these reactions, a change in pressure changes concentration because the partial pressure of an ideal gas is proportional to its molar concentration. That means pressure changes affect equilibrium in the same way as concentration changes. When the volume of a gas mixture changes, the concentrations of reactants and products change together. Since every gas in the equilibrium occupies the same space, the same volume change...

le chatelier's principle: changing temperature

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Le Chatelier's Principle in Heating and Cooling

Le Chatelier's principle helps explain how chemical equilibrium responds to heating and cooling. A system at equilibrium will shift to restore balance after a temperature change, but the equilibrium constant, K, will not stay the same. Instead, the mixture reaches a new equilibrium with a different composition. This temperature effect is different from a concentration change, which shifts equilibrium without changing K. To understand why temperature matters, the reaction can be written with...

the small x assumption

Estimating Equilibrium with Small Changes

A small equilibrium constant can make equilibrium calculations easier. In these reactions, the equilibrium position favors the reactants. When the initial reactant concentration is high and the Kc value is small, the change in concentration may be negligible. In that case, the equilibrium concentration is close to the initial concentration. This idea helps simplify weak acid and weak base problems. Chemists can assume that some equilibrium concentrations are equal to the initial concentrations.

key terms and concepts

Learn how changing volume changes pressure and concentration in gas-phase equilibrium, and why stoichiometry decides whether the system shifts left or right.

Gas Equilibrium Under Volume Changes | JoVE K12

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Gas Equilibrium Under Volume Changes

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