Name: shifting equilibrium by changing concentration
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Le Chatelier's Principle: Changing Concentration

İleri reaksiyonun hızı, ters reaksiyonun hızına eşit olduğunda, bir sistem dinamik denge içindedir. Reaksiyon her iki yönde de devam etse de, reaktanların ve ürünlerin net konsantrasyonları sabit kalır. Bu noktada, örneğin ilave A molekülü ekleyerek veya bir miktar C molekülü çıkararak bir reaktan veya ürünün konsantrasyonu değiştirilirse denge bozulur.Bu tür değişiklikler sistem üzerindeki baskılardır. Le Châtelier ilkesine göre, konsantrasyondaki bir değişiklik, hacim veya basınçtaki bir değişiklik veya sıcaklıktaki bir değişiklik nedeniyle dengede bir sistem gerildiğinde, denge konumu, gerilimi en aza indirecek ve dengeyi yeniden sağlayacak bir yönde kayar. Bir sistemin konsantrasyondaki değişikliklere tepkisini anlamak için birbirine bağlı A ve B adındaki iki su tankını düşünün.Başlangıçta, iki tanktaki su seviyesi eşittir ve sistem dengededir. Daha sonra B tankına su eklenir. Bu değişiklik B tankındaki su seviyesini yükseltir ve dengeyi bozar.Bu değişikliği dengelemek için, suyun bir kısmı dengeyi yeniden sağlamak amacıyla A tankına akar. Tersine, B tankından su çekilirse su seviyesinin düşürülmesi de değişikliği tetikler. Sonuç olarak, dengeyi yeniden sağlamak için A tankından gelen su B tankına akar.Dengedeki bir sistem için, reaksiyon katsayısı denge sabitine eşittir. Denge karışımına daha fazla reaktan eklemek Q'yu azaltır. Le Châtelier ilkesine göre, sistem, eklenen reaktanı harcamak ve dengeyi yeniden kurmak için denge konumunu ürünlere doğru kaydırarak bu değişikliği en aza indirir.Aynı şekilde, denge karışımından bir ürünün çıkarılması, dengeyi yeniden sağlamak için benzer bir tepkiye yol açacaktır. Aksine, daha fazla ürün eklemek Q'yu artırır. Bu nedenle, denge konumu, eklenen ürünü tüketmek ve dengeyi yeniden sağlamak için reaktanlara doğru kayar.Yoğunlaşmadaki bir değişiklik, K'nin değerini değiştirmeden denge konumunu değiştirir.

le chatelier prensibi: konsantrasyon değiştirme

Dengedeki bir sistem, ileri ve geri reaksiyonların eşit oranlarda gerçekleştiği dinamik bir denge halindedir. Bir denge sistemi, bu reaksiyon hızlarını farklı şekilde etkileyen koşullarda bir değişikliğe maruz kalırsa (bir stres), oranlar artık eşit değildir ve sistem dengede değildir. Sistem daha sonra dengeyi yeniden kuracak daha büyük bir hız (bir kayması) yönünde net bir reaksiyon yaşayacaktır. Bu fenomen Le Châteliers prensibi ile özetlenmiştir:bir denge sistemi strese maruz bırakılırsa, sistem dengeyi yeniden kuran strese yanıt olarak bir kayma yaşayacaktır.
 
 Reaksiyon hızları birincil olarak reaksiyonun hız yasasında açıklandığı gibi konsantrasyonlardan ve Arrhenius denkleminde açıklandığı gibi sıcaklıktan etkilenir. Sonuç olarak, konsantrasyon ve sıcaklıktaki değişiklikler, bir dengeyi değiştirebilen iki strestir.
 
 Konsantrasyon Değişikliğinin Etkisi
 
 Bir denge sistemi, bir reaktan veya ürün türünün konsantrasyonunda bir değişikliğe maruz kalırsa, ileri veya ters reaksiyonun hızı değişecektir. Örnek olarak, denge reaksiyonunu düşünün:
 
 <img alt=""Eq1"" src=""/files/ftp_upload/11391/11391_Equation 1v2.png"" style=""text-align: center; height: 48px;"" />
 
 Bu sistem dengede olduğunda, ileri ve geri reaksiyon oranları eşittir.
 
 <img alt=""Eq2"" src=""/files/ftp_upload/11391/11391_Equation 2.png"" style=""text-align: center; height: 50px;"" />
 
 Sistem, N2 veya O2 reaktan eklenerek strese maruz bırakılırsa, konsantrasyondaki ortaya çıkan artış, ters reaksiyonun hızını aşarak ileri reaksiyon oranının artmasına neden olur:
 
 <img alt=""Eq3"" src=""/files/ftp_upload/11391/11391_Equation 3.png"" style=""text-align: center; height: 50px;"" />
 
 Sistem dengeyi yeniden kurmak için ileri yönde geçici bir net reaksiyon yaşayacaktır (denge sağa kayacaktır ). Bu aynı kayma, sistemden bir miktar NO ürününün çıkarılması durumunda ortaya çıkacaktır, bu da ters reaksiyonun oranını düşürür ve yine oranlarda aynı dengesizliğe neden olur.
 
 Aynı mantık, reaktanın çıkarılmasından veya bir denge sistemine ürün eklenmesinden kaynaklanan sola kaymayı açıklamak için kullanılabilir. Bu streslerin her ikisi de ters reaksiyon için artan bir oranla 
 
 <img alt=""Eq4"" src=""/files/ftp_upload/11391/11391_Equation 4.png"" style=""text-align: center; height: 50px;"" />
 
 ve dengeyi yeniden kurmak için ters yönde geçici bir net reaksiyonla sonuçlanır.
 
 Bu kinetik yoruma bir alternatif olarak, konsantrasyondaki değişikliklerin denge üzerindeki etkisi, reaksiyon katsayısı açısından rasyonelleştirilebilir. Sistem dengede olduğunda,
 
 <img alt=""Eq5"" src=""/files/ftp_upload/11391/11391_Equation 5.png"" style=""text-align: center; height: 70px;"" />
 
 Bir reaktan eklenirse (reaksiyon bölümünün paydasını arttırırsa) veya ürün çıkarılırsa (payın azaltılması), o zaman Qc < Kc ve denge sağa kayacaktır. Bu stresi indüklemenin üç farklı yolunun, denge karışımının bileşiminde üç farklı değişikliğe neden olduğunu unutmayın. N2 eklenirse, sağ kayma O2 tüketecek ve denge yeniden kuruldukça NO üretecek ve daha önce mevcut olandan daha yüksek N2 ve NO konsantrasyonuna ve daha az O2 konsantrasyonuna sahip bir karışım verecek. O2 eklenirse, yeni denge karışımı daha yüksek O2 ve NO konsantrasyonlarına ve daha az N2 konsantrasyonuna sahip olacaktır. Son olarak, NO çıkarılırsa, yeni denge karışımı daha yüksek N2 ve O2 konsantrasyonlarına ve daha az NO konsantrasyonuna sahip olacaktır. Bileşimdeki bu farklılıklara rağmen, denge sabitinin değeri, stresten sonra eskisi ile aynı olacaktır (kütle eylem yasasına göre). Aynı mantık, reaktanların çıkarılmasını veya ürün eklenmesini içeren stresler için de uygulanabilir; bu durumda Qc> Kc ve denge sola kayacaktır.
 
 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: Konsantrasyon Değiştirme

Dengedeki bir sistem, ileri ve geri reaksiyonların eşit oranlarda gerçekleştiği dinamik bir denge durumundadır. Eğer bir denge sistemi ...

Education

JoVE Core

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Chemical Equilibrium

Kimyasal Denge

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

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 reactant or product can move the equilibrium in one direction or the other.

Adding a reactant, such as N2 or O2 in the example reaction, increases the forward reaction rate. The forward rate then becomes greater than the reverse rate, so the equilibrium shifts right. Removing the product NO has the same effect because it lowers the reverse reaction rate and creates the same imbalance.

The opposite changes cause a left shift. Removing reactant or adding product increases the reverse reaction rate compared with the forward rate. The system then moves in the reverse direction until equilibrium is reached again.

This shift can also be explained with the reaction quotient, Qc, and the equilibrium constant, Kc. When reactant is added, Qc becomes less than Kc. When product is removed, Qc also becomes less than Kc, so the equilibrium shifts right. If reactant is removed or product is added, then Qc is greater than Kc and the equilibrium shifts left.

Although the final composition changes, the equilibrium constant stays the same after the stress is removed and the system rebalances. If N2 is added, the new mixture has more N2 and NO and less O2. If O2 is added, the mixture has more O2 and NO and less N2. If NO is removed, the mixture ends with more N2 and O2 and less NO. The same idea applies to shifts caused by removing reactant or adding product.

Shifting Equilibrium by Changing Concentration

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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

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...

calculating the equilibrium constant

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...

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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)

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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...

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...

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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 concentration shifts chemical equilibrium, including why adding or removing reactants or products moves the reaction left or right.

Shifting Equilibrium by Changing Concentration | JoVE K12

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Shifting Equilibrium by Changing Concentration

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