Henderson-Hasselbalch equation defined

Acids will dissociate into hydrogen ions, i.e., protons, and their matching anions. Bases will dissociate into a cation and a hydroxyl anion. If the acid or base is a strong acid or strong base, then the dissociation is complete. Weak acids and weak bases dissociate only partially. How much is defined by the dissociation constant of the acid or base. When expressed as the negative logarithm of the proton concentration in equivalents/liter, it is called the pK of the acid or base. Therefore, in a solution of a weak acid, three participants are present proton, matching anion, and the undissociated parent weak acid. Similarly, a solution of a weak base contains a cation, a hydroxyl anion, and the undissociated parent base. How much of each is defined by the pH of the solution and the pK of the respective acid or base The Henderson-Hasselbalch equation defines the relationship ... 

The answer is D. Weak acids like lactic acid never completely dissociate in solution and are thus defined by the property that at least some of the protonated (undissociated acid) form and the unprotonated (conjugate base) form of the acid are present at all concentrations and pH conditions. The indicated of 5.2 is consistent with the idea that the lactate anion retains a strong affinity for protons, a hallmark of a weak acid. The lactate anion is highly water-soluble. All weak acids obey the Henderson-Hasselbalch equation. 

Equation 2.6 is the familiar Henderson-Hasselbalch equation, which defines the relationship between pH and the ratio of acid and conjugate base concentrations. The Henderson-Hasselbalch equation is of great value in buffer chemistry because it can be used to calculate the pH of a solution if the molar ratio of buffer ions ([A-]/[HA]) and the pKa of HA are known. Also, the molar ratio of HA to A- that is necessary to prepare a buffer solution at a specific pH can be calculated if the pKa is known. 

The buffer capacity is defined as the number of moles per litre of strong monobasic acid or base required to produce an increase or decrease of one pH unit in the solution. When the concentrations of salt and acid are equal, the log term in the Henderson-Hasselbalch equation becomes the logarithm of 1, which equals 0. To move the pH of the buffer solution by one unit of pH will require the Henderson-Hasselbalch equation to become... 

Buffers are defined as substances that resist changes in the pH of a system. All weak acids or bases, in the presence of their salts, form buffer systems. The action of buffers and their role in maintaining the pH of a solution can best be explained with the aid of the Henderson-Hasselbalch equation, which may be derived as follows. 

In 1916 Hasselbalch showed that a logarithmic transformation of the equation was a more useful form, and used the symbols pH (= -logcH ) and pK (= -logiC. pH is defined as the negative log of the activity of (flH ), which is the entity actually measured with pH meters. The resulting Henderson-Hasselbalch equation becomes... 

Bicarbonate is the second largest fraction (behind Ci ) of plasma anions ( 25 mmol/L). Conventionally, it is defined to include (1) plasma bicarbonate ion, (2) carbonate, and (3) CO2 bound in plasma carbamino compounds (Figure 46-7). At the pH of blood, the plasma carbonate concentration is 25 pmol/L, which is -1/700 to 1/1000 of the total bicarbonate concentration. C02-bound carbamino compounds (RCNHCOOH) are 0.2 mmol/L in plasma and 1.5 mmol/L in erythrocytes. Actual bicarbonate ion concentration is not measured, but rather calculated from the Henderson-Hasselbalch equation as described below (and discussed in detail in Chapter 27). Also, as described in Chapter 27, the analyte usually measured in plasma is total COa, which includes bicarbonate and dissolved CO (dC02). The dC02 fraction is defined to include both the undissociated carbonic acid and physically dissolved, free CO2. At the pH of the blood, the amount of dissolved CO2 is 700 to 1000 times greater than the amount of carbonic acid and therefore... 

The buffer value (p) is defined as the amount of base required to cause a change in pH of one unit. The buffer value of the bicarbonate buffer in plasma is 55.6 mmol/L. Derivation of this value is obtained by taking partial differentials of the Henderson-Hasselbalch equation, which is presented in detail in the second edition of this textbook. ... 

The acidity or basicity of a drug substance is defined by the dissociation constant K, which is the equilibrium constant, more conveniently represented by its logarithmic parameter pK, reflecting the degree of ionization of a substance at a particular pH and described by the Henderson-Hasselbalch equations (37.2) and (37.3). ... 

The answer is a. (Murray pp 15-26.) The equilibrium between an acid and its conjugate base is defined by the Henderson-Hasselbalch equation ... 

The Henderson-Hasselbalch equation can be derived from the expression that defines the acid dissociation constant ... 

Experimental measurements of solubility are influenced by many different factors, including the purity of the solute and solvent, presence of cosolvents, presence of salts, temperature, physical form of the undissolved solute, ionization state, and solution pH [18]. Consequently many different definitions of solubility are in common use in the published literature. Here we discuss the intrinsic aqueous solubility, Sg, which is defined as the concentration of the neutral form of the molecule in saturated aqueous solution at thermodynamic equilibrium at a given tanperature [18-20]. Intrinsic aqueous solubility is used to calculate dissolution rate and pH-dependent solubility in models such as the Noyes-Whimey equation [21] and the Henderson-Hasselbalch equation [22, 23], respectively. Prediction of the intrinsic aqueous solubility of bioactive molecules is of great importance in the biochemical sciences because it is a key determinant in the bioavailability of novel pharmaceuticals [1, 3, 24-26] and the environmental fate of potential pollutants [27, 28],... 

The degree of dissociation, on the other hand, depends, in a well-defined manner, on the p T of the analyte and the pH of the solution, according to the Henderson-Hasselbalch equation, a, is a function of p Ta and pH for example, for monobasic neutral acids... 

The use of the prime in pK. This is used as defined in the present text to indicate the pK value when the concentration of CO2 is used rather than that of H2CO3 in the Henderson-Hasselbalch equation. Physical chemists use the prime for a different purpose. They use pK for the constant expressed in terms of concentration and pK for the constant expressed in terms of activities, i.e. as actually measured experimentally. 

Define buffer capadty. Mention Henderson-Hasselbalch equation. 

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