Name: le chatelier's principle in heating and cooling
Uploaded: 2020-09-24T15:06:51.000Z
Duration: 2 min 19 s
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Le Chatelier's Principle: Changing Temperature

Sıcaklık, kimyasal bir reaksiyonun oranını etkiler;bu nedenle, dengede bir reaksiyon için sıcaklıktaki bir değişiklik, sistem üzerinde bir baskı görevi görür. Le Châtelier'in prensibi, sistemin bu tür karışıklıkları en aza indirmek için nasıl tepki vereceğini öngörür. Sıcaklıktaki bir değişiklik, K'nin değerini değiştirmeden dengeyi değiştiren konsantrasyon veya hacimdeki bir değişikliğin aksine, denge sabitinin değerini değiştirir.Gaz halindeki fosfor pentaklorürün fosfor triklorür ve klor gazına ayrışmasını düşünün. Bu endotermik reaksiyon için, emilen ısı bir reaktan olarak düşünülebilir. Sıcaklıktaki artış, daha fazla reaktan eklemeye benzer şekilde sisteme ısı ekler.Bu nedenle, denge konumu ürünlere doğru kayar ve ekstra ısıyı tüketmek için daha fazla fosfor triklorür ve klor üretir çünkü denge sabiti K değeri artmıştır. Öte yandan, sıcaklıktaki bir azalma, bir reaktanın çıkarılmasına benzer şekilde, ısıyı sistemden uzaklaştırır. Denge konumu reaktanlara doğru kayar ve ısıyı serbest bırakmak için daha fazla fosfor pentaklorür üretir çünkü K değeri azalmıştır.Kükürt dioksit ile oksijen arasındaki gaz reaksiyonu gibi kükürt trioksit üretmek için ekzotermik bir reaksiyon için açığa çıkan ısı bir ürün olarak düşünülebilir. Sıcaklıktaki artış, daha fazla ürün eklemeye benzer. Bu, denge pozisyonunun reaktanlara doğru kaymasına neden olarak, eklenen ısının bir kısmını absorbe etmek için daha fazla kükürt dioksit ve oksijen üretir, çünkü K değeri azalmıştır.Tersine, bu ekzotermik reaksiyonun sıcaklığını düşürmek, bir ürünü çıkarmak gibi ısıyı ortadan kaldırır. Denge konumu ürünlere doğru kayar ve K arttıkça ısıyı serbest bırakmak için daha fazla kükürt trioksit üretir. Bu nedenle, sıcaklıktaki bir artış, endotermik bir reaksiyondaki ürünleri desteklerken, sıcaklıktaki bir azalma, bir ekzotermik reaksiyondaki ürünleri destekler.

le chatelier prensibi: sıcaklık değiştirme

Kütle eylem yasasına uygun olarak, konsantrasyondaki bir değişiklikle vurgulanan bir denge, denge sabiti K değerinde herhangi bir değişiklik olmaksızın dengeyi yeniden kurmak için kayacaktır. Bununla birlikte, bir sıcaklık değişikliğine yanıt olarak bir denge kayması olduğunda, denge sabiti için farklı bir değer sergileyen farklı bir bağıl bileşim ile yeniden kurulur.
 
 Bu fenomeni anlamak için temel reaksiyonu göz önünde bulundurun:
 
  <img alt=""Eq1"" src=""/files/ftp_upload/11393/11393_Equation_1.png"" style=""height: 50px;"" />
 
 Bu temel bir reaksiyon olduğundan, ileri ve geri için oran yasaları doğrudan dengeli denklemin stokiyometrisinden türetilebilir:
 
  <img alt=""Eq2"" src=""/files/ftp_upload/11393/11393_Equation_2.png"" style=""height: 65px;"" />
 
 Sistem dengede olduğunda,
 
  <img alt=""Eq3"" src=""/files/ftp_upload/11393/11393_Equation_3.png"" style=""height: 50px;"" />
 
 Oran yasalarının bu eşitlikle değiştirilmesi ve yeniden düzenlenmesi
 
  <img alt=""Eq4"" src=""/files/ftp_upload/11393/11393_Equation_4.png"" style=""height: 100px;"" />
 
 Denge sabiti, ileri ve geri reaksiyonlar için hız sabitlerinin matematiksel bir fonksiyonu olarak ifade edilebilir. Hız sabitleri Arrhenius denklemi tarafından tanımlandığı gibi sıcaklıkla değiştiğinden, denge sabitinin benzer şekilde sıcaklıkla değişeceği mantıklıdır (hız sabitlerinin sıcaklık değişiminden farklı düzeylerde etkilendiği varsayılırsa). Çok adımlı reaksiyon mekanizmalarını içeren daha karmaşık reaksiyonlar için, benzer ancak daha karmaşık bir matematiksel ilişki, mekanizmadaki adımların denge sabiti ile hız sabitleri arasında mevcuttur. Reaksiyon ne kadar karmaşık olursa olsun, denge sabitinin sıcaklığa bağımlılığı devam eder.
 
 Sıcaklıktaki bir değişime tepki olarak bir dengenin yaşayacağı kaymayı tahmin etmek, en uygun şekilde reaksiyonun entalpi değişimi dikkate alınarak gerçekleştirilir. Örneğin, Haber süreci ile amonyak oluşumu ekzotermik (ısı üreten) bir süreçtir:
 
  <img alt=""Eq5"" src=""/files/ftp_upload/11393/11393_Equation_5.png"" style=""height: 50px;"" />
 
 Le Châtelier prensibinin uygulanması amacıyla ısı, q, bir ürün olarak görülebilir:
 
  <img alt=""Eq6"" src=""/files/ftp_upload/11393/11393_Equation_6.png"" style=""height: 50px;"" />
 
 Sistemin sıcaklığını yükseltmek, bir ürünün miktarını artırmaya benzer ve bu nedenle denge sola kayar. Sistem sıcaklığının düşürülmesi de aynı şekilde dengenin sağa kaymasına neden olacaktır. Endotermik süreçler için ısı, reaksiyonun bir reaktanı olarak görülür ve bu nedenle ters sıcaklık bağımlılığı gözlemlenir.
 
 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: Le </a><a href=""https://openstax.org/books/chemistry-2e/pages/13-3-shifting-equilibria-le-chateliers-principle"">Ch</a>â<a href=""https://openstax.org/books/chemistry-2e/pages/13-3-shifting-equilibria-le-chateliers-principle"">t</a><a href=""https://openstax.org/books/chemistry-2e/pages/13-3-shifting-equilibria-le-chateliers-principle"">elier’s Principle</a>.

Le Chatelier Prensibi: Sıcaklık Değiştirme

Kütle hareketi yasasıyla tutarlı olarak, konsantrasyondaki bir değişiklikle vurgulanan bir denge, herhangi bir değişiklik olmaksızın dengeyi yeniden kurmak için değişecektir.

Education

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Chemical Equilibrium

Kimyasal Denge

KEY TERMS AND CONCEPTS

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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 forward and reverse rate laws based on the balanced equation. At equilibrium, the forward and reverse reaction rates are equal. When those rate laws are combined and rearranged, the equilibrium constant can be expressed as a function of the forward and reverse rate constants.

Because rate constants change with temperature, as described by the Arrhenius equation, the equilibrium constant can also change with temperature. This idea applies to both elementary reactions and more complex multistep mechanisms. In multistep reactions, the math is more complicated, but the temperature dependence of the equilibrium constant still remains.

A practical way to predict the direction of the shift is to use the reaction’s enthalpy change. In the Haber process, ammonia formation is exothermic, which means it produces heat. For Le Chatelier's principle, heat can be treated like a product. Raising the temperature adds heat, so the equilibrium shifts left. Lowering the temperature removes heat, so the equilibrium shifts right. For endothermic processes, heat acts like a reactant, so the temperature effect is opposite.

Le Chatelier's Principle in Heating and Cooling

le-chateliers-principle-heating-and-cooling

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...

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...

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...

calculating equilibrium concentrations

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

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 heating and cooling change chemical equilibrium, why K changes with temperature, and how exothermic and endothermic reactions shift.

Le Chatelier's Principle in Heating and Cooling | JoVE K12

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Le Chatelier's Principle in Heating and Cooling

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