Name: buffer ph with the henderson-hasselbalch equation
Uploaded: 2020-09-24T15:06:51.000Z
Duration: 2 min 48 s
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Henderson-Hasselbalch Equation

Bir eşlenik asit-baz çifti içeren tamponlu bir çözeltinin pH'ı, bir ICE tablosuna alternatif olarak Henderson-Hasselbalch denklemi kullanılarak hesaplanabilir. Henderson-Hasselbalch denklemi, Ka için denge sabiti ifadesinden türetilmiştir. Bu ifade, hidronyum iyon konsantrasyonunu belirlemek için yeniden düzenlenebilir.Her iki tarafın negatif logu alınırsa, hidronyum iyon konsantrasyonunun negatif logaritması ve asit ayrışma sabitinin negatif logaritması sırasıyla pH ve pKa ile değiştirilebilir. Bu, bir tamponun pH'ının, pKa ve onun zayıf asidinin üzerine bir konjugat bazın denge konsantrasyonlarının logaritması eklenerek hesaplanabildiği bir denklem verir. Hidronyum iyon konsantrasyonundaki değişiklik x, hem zayıf asit hem de eşlenik bazın başlangıç konsantrasyonlarının yüzde 5'inden azsa, bu denge değerleri başlangıç konsantrasyonları ile değiştirilebilir.Henderson-Hasselbalch denklemi, belirli bir pH'ta bir tampon hazırlamak için gereken bazın aside oranını da gösterir. Benzer şekilde, zayıf bir baz ve bunun eşlenik asidini içeren bir çözeltinin pH'ı, aşağıdaki formül kullanılarak pKb'den konjugat asidin pKa'sı hesaplanarak bu denklem kullanılarak belirlenebilir:pKa artı pKb on dörde eşittir. 0, 15 molar formik asit ve 0, 18 molar sodyum format içeren bir tamponun pH'ı, Henderson-Hasselbalch denklemi veya formik asit için Ka ve ICE tablosu kullanılarak belirlenebilir.Bununla birlikte, Henderson-Hasselbalch denklemi, bir reaksiyon bir konjuge asit-baz çifti içerdiğinde ve hidronyum konsantrasyonundaki değişiklik küçük olduğunda pH'ı hesaplamak için daha hızlı bir yöntemdir. PKa, formik asit için Ka'nın 3, 75'e eşit olan negatif logaritması alınarak belirlenir. Formik asit ve formatın başlangıç konsantrasyonları denkleme eklendiğinde, çözelti için pH değeri 3, 83'e eşittir.Bu pH değeri, hidronyum iyon konsantrasyonunu 1, 5×10⁻⁴ belirlemek için kullanılabilir. Bu değer 0, 15 molar formik asidin yüzde 5'inden az olduğundan, Henderson-Hasselbalch denklemini kullanmak için gerekli olan yaklaşımlar geçerlidir.

De Levie, Robert. "Henderson-Hasselbalch denklemi: tarihi ve sınırlamaları." Kimya Eğitimi Dergisi 80, hayır. 2 (2003): 146. <a href="https://pubs.acs.org/doi/pdf/10.1021/ed080p146">https://pubs.acs.org/doi/pdf/10.1021/ed080p146.</a>

henderson-hasselbalch denklemi

Zayıf bir asit çözeltisinin iyonizasyon sabiti ifadesi şu şekilde yazılabilir:
 
 <img alt=""Eq1"" src=""/files/ftp_upload/11410/11410_Equation_1.png"" style=""text-align: center; height: 90px;"" />
 
 [H3O+]’yi çözmek üzere yeniden düzenleme şu sonuçları verir:
 
 <img alt=""Eq2"" src=""/files/ftp_upload/11410/11410_Equation_2.png"" style=""text-align: center; height: 90px;"" />
 
 Bu denklemin her iki tarafının negatif logaritmasını almak şunu verir
 
 <img alt=""Eq3"" src=""/files/ftp_upload/11410/11410_Equation_3.png"" style=""text-align: center; height: 90px;"" />
 
 şu şekilde yazılabilir:
 
 <img alt=""Eq4"" src=""/files/ftp_upload/11410/11410_Equation_4.png"" style=""text-align: center; height: 90px;"" />
 
 Burada pKa, zayıf asidin iyonizasyon sabitinin logaritmasının negatifidir (pKa = −log Ka). Bu denklem, pH, zayıf bir asidin iyonizasyon sabiti ve tamponlu bir çözelti içindeki zayıf eşlenik asit-baz çiftinin konsantrasyonları ile ilgilidir. Bilim adamları genellikle Henderson-Hasselbalch denklemi adı verilen bu ifadeyi tampon çözeltilerin pH'sını hesaplamak için kullanırlar. Bu denklemi kullanmak için “x küçüktür” varsayımının geçerli olması gerektiğine dikkat etmek önemlidir.
 
 Lawrence Joseph Henderson ve Karl Albert Hasselbalch
 
 Lawrence Joseph Henderson (1878–1942), birçok ilgi alanından sadece birkaçını isimlendirmek gerekirse, Amerikalı bir doktor, biyokimyacı ve fizyologdu. Harvard'dan tıp diploması aldı ve ardından Harvard'da öğretim görevlisi olarak görev almak için dönmeden önce 2 yıl Strasbourg'da, ardından Almanya'nın bir bölümünde eğitim gördü. Sonunda Harvard'da profesör oldu ve hayatı boyunca orada çalıştı. İnsan kanındaki asit-baz dengesinin, kanda çözünmüş karbondioksitin oluşturduğu bir tampon sistemi tarafından düzenlendiğini keşfetti. 1908'de kandaki karbonik asit-karbonat tampon sistemini tanımlamak için bir denklem yazdı. Henderson çok bilgiliydi; kan fizyolojisi üzerine yaptığı önemli araştırmasının yanı sıra organizmaların adaptasyonları ve çevrelerine uyumu, sosyoloji ve üniversite eğitimi üzerine de yazdı. Ayrıca Harvard Business School'da, endüstri, egzersiz ve beslenmedeki çalışmaya özel olarak odaklanarak insan fizyolojisini inceleyen Yorgunluk Laboratuvarı'nı kurdu.
 
 1916'da, Danimarkalı bir doktor ve kimyager olan Karl Albert Hasselbalch (1874–1962), 1904'te Christian Bohr ile kandaki hemoglobinin oksijen ile bağlanma yeteneğinin kanın asitliği ve karbondioksit konsantrasyonu ile ters orantılı olduğunu gösteren Bohr etkisini anlatan bir makalede yazarlığı paylaştı. pH ölçeği, 1909'da Dane, Sørensen tarafından tanıtıldı ve 1912'de Hasselbalch, kanın pH ölçümlerini yayınladı. 1916'da Hasselbalch, Henderson denklemini logaritmik olarak pH'nın logaritmik ölçeğiyle uyumlu olarak ifade etti ve böylece Henderson-Hasselbalch denklemi doğdu.
 
 Bu metin bu kaynaktan uyarlanmıştır: <a href=""https://openstax.org/books/chemistry-2e/pages/14-6-buffers""> Openstax, Chemistry 2e, Section 14.6: Buffers</a>.

Henderson-Hasselbalch Denklemi

Zayıf bir asidin çözeltisi için iyonlaşma sabiti ifadesi şu şekilde yazılabilir:

[H3O+] verimlerini çözmek için yeniden düzenleme:

Negatifi almak ...

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Acid-base and Solubility Equilibria

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buffer ph with the henderson-hasselbalch equation

The Henderson-Hasselbalch equation helps relate buffer pH to the weak acid in the solution. It comes from the ionization-constant expression for a weak acid. By rearranging that expression to solve for hydronium ion concentration, [H3O+], and then taking the negative logarithm of both sides, the equation can be written in terms of pH.

In this form, pKa is defined as the negative logarithm of the weak acid ionization constant, or pKa = −log Ka. The equation shows the connection between pH, pKa, and the concentrations of a weak conjugate acid-base pair in a buffered solution. Scientists often use this relationship to calculate the pH of buffer solutions.

A key condition is that the “x is small” assumption must be valid before the equation is used. If that assumption does not hold, the result may not be reliable. The equation is a practical shortcut, but it depends on the chemistry of the weak acid system.

The equation is named for Lawrence Joseph Henderson and Karl Albert Hasselbalch. Henderson was an American physician, biochemist, and physiologist who studied the carbonic acid-carbonate buffer system in blood and wrote an equation for it in 1908. He also worked on organisms and their environment, sociology, university education, and the Fatigue Laboratory at Harvard Business School, which studied human physiology in industry, exercise, and nutrition.

Hasselbalch was a Danish physician and chemist who helped connect this idea to the pH scale. The pH scale was introduced in 1909 by Sørensen, and Hasselbalch later published measurements of blood pH in 1912. In 1916, he rewrote Henderson’s equation in logarithmic form, which matched the logarithmic pH scale. That is how the Henderson-Hasselbalch equation was born.

Buffer pH with the Henderson-Hasselbalch Equation

buffer-ph-with-the-henderson-hasselbalch-equation

common ion effect

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titration calculations: strong acid - strong base

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titration calculations: weak acid - strong base

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henderson-hasselbalch equation

The Henderson-Hasselbalch equation helps relate buffer pH to the weak acid in the solution. It comes from the ionization-constant expression for a weak acid. By rearranging that expression to solve for hydronium ion concentration, [H3O+], and then taking the negative logarithm of both sides, the equation can be written in terms of pH. In this form, pKa is defined as the negative logarithm of the weak acid ionization constant, or pKa = −log Ka. The equation shows the connection between pH, pKa,...

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key terms and concepts

Learn how the Henderson-Hasselbalch equation links buffer pH, pKa, and weak acid-base pair concentrations, and why the small-x assumption matters.

Buffer pH with the Henderson-Hasselbalch Equation | JoVE K12

chemistry

JoVE Core Kimya, özlü ve kolay anlaşılır animasyon video derslerini kullanarak genel kimya kavramlarına hayat veriyor. Ek olarak, bilim insanı uygulama videolarımız ile klasik ve orijinal araştırma deneylerini dünya çapında günümüz laboratuvarlarında görselleştiriyoruz.

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Content elaboration: In the Physical Science course, coefficients were used to balance simple equations. Other representations, including Lewis structures and three-dimensional models, were also used and manipulated to demonstrate the conservation of matter in chemical reactions. In this course, more complex reactions will be studied, classified and represented with balanced chemical equations and three-dimensional models. Classifying reactions into types can be a helpful organizational tool for recognizing patterns of what may happen when two substances are mixed. Teachers should be aware that the common reaction classifications that are often used in high school chemistry courses may lead to misconceptions because they are not based on the actual chemistry, but on surface features that can be similar from one system to another (e.g., exchanging partners), even though the underlying chemistry is not the same. 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Organic molecules release energy when undergoing combustion reactions and are used to meet the energy needs of society (e.g., oil, gasoline, natural gas) and to provide the energy needs of biological organisms (e.g., cellular respiration). When a reaction between two ionic compounds in aqueous solution results in the formation of a precipitate or molecular compound, the reaction often occurs because the new ionic or covalent bonds are stronger than the original ion-dipole interactions of the ions in solution. Laboratory experiences (3-D or virtual) with different types of chemical reactions should be provided. Reactions occur when reacting particles collide in an appropriate orientation and with sufficient energy. The rate of a chemical reaction is the change in the amount of the reactants or products in a specific period of time. Increasing the probability or effectiveness of the collisions between the particles increases the rate of the reaction. Therefore, changing the concentration of the reactants, changing the temperature or the pressure of gaseous reactants, or using a catalyst, can change the reaction rate. Likewise, the collision theory can be applied to dissolving solids in a liquid solvent and can be used to explain why reactions are more likely to occur between reactants in the aqueous or gaseous state than between solids. The rate at which a substance dissolves should not be confused with the amount of solute that can dissolve in a given amount of solvent (solubility). Mathematical treatment of reaction rates is reserved for more advanced study. Computer simulations can help visualize reactions from the perspective of the kinetic-molecular theory. In middle school, the differences between potential and kinetic energy and the particle nature of thermal energy were introduced. For chemical systems, potential energy is in the form of chemical energy and kinetic energy is in the form of thermal energy. The total amount of chemical energy and/or thermal energy in a system is impossible to measure. However, the energy change of a system can be calculated from measurements (mass and change in temperature) from calorimetry experiments in the laboratory. Conservation of energy is an important component of calorimetry equations. Thermal energy is the energy of a system due to the movement of its particles. The thermal energy of an object depends upon the temperature and chemical composition. Some materials require little energy to change their temperature and other materials require a great deal to change their temperature by the same amount. Specific heat is a measure of how much energy is needed to change the temperature of a specific mass of material a specific amount. Specific heat values can be used to calculate the thermal energy change, the temperature (initial, final or change in) or mass of a material in calorimetry. Water has a particularly high specific heat capacity, which is important in regulating Earth's temperature. As studied in middle school, chemical energy is the potential energy associated with chemical systems. Chemical reactions involve valence electrons forming bonds to yield more stable products with lower energies. Energy is required to break interactions and bonds between the reactant atoms and energy is released when an interaction or bond is formed between the atoms in the products. Molecules with weak bonds (e.g., ATP) are less stable and tend to react to produce more stable products, releasing energy in the process. Generally, energy is transferred out of the system (exothermic) when the products have stronger bonds than the reactants and is transferred into the system (endothermic) when the reactants have stronger bonds than the products. Predictions of the energy requirements (endothermic or exothermic) of a reaction can be made given a table of bond energies. Graphic representations can be drawn and interpreted to represent the energy changes during a reaction. The role of energy in determining the spontaneity of chemical reactions is dealt with conceptually in this course. Entropy and its influence on the spontaneity of reactions are reserved for more advanced study. All reactions are reversible to a degree and many reactions do not proceed completely toward products but appear to stop progressing before the reactants are all used up. At this point, the amounts of the reactants and the products appear to be constant and the reaction can be said to have reached dynamic equilibrium. Dynamic equilibrium means the rate of the reverse reaction is equal to the rate of the forward reaction so there is no apparent change in the reaction. If a chemical system at equilibrium is disturbed by a change in the conditions of the system (e.g., increase or decrease in the temperature, pressure on gaseous equilibrium systems, concentration of a reactant or product), then the equilibrium system will respond by shifting to a new equilibrium state, reducing the effect of the change (Le Chatelier's Principle). If products are removed as they are formed during a reaction, then the equilibrium position of the system is forced to shift to favor the products. In this way, an otherwise unfavorable reaction can be made to occur. Mathematical treatment of equilibrium reactions is reserved for advanced study. Computer simulations can help visualize the progression of a reaction to dynamic equilibrium and the continuation of both the forward and reverse reactions after equilibrium has been attained. Properties of acids and bases and the ranges of the pH scale were introduced in Physical Science. In this course, the structural features of molecules are explored to further understand acids and bases. Acids often result when hydrogen is covalently bonded to an electronegative element and is easily dissociated from the rest of the molecule to bind with water to form a hydronium ion (H3O+). The acidity of an aqueous solution can be expressed as pH, where pH can be calculated from the concentration of the hydronium ion. Bases are likely to dissociate in water to form a hydroxide ion. Acids can react with bases to form a salt and water. Such neutralization reactions can be studied quantitatively by performing titration experiments.

Buffer pH with the Henderson-Hasselbalch Equation

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