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% species formation calculated with the program HySS for a 10 millimolar solution of citric acid. pK a1 = 3.13, pK a2 = 4.76, pK a3 = 6.40. When the difference between successive pK values is less than about four there is overlap between the pH range of existence of the species in equilibrium. The smaller the difference, the more the overlap.
A simple buffer solution consists of a solution of an acid and a salt of the conjugate base of the acid. For example, the acid may be acetic acid and the salt may be sodium acetate . The Henderson–Hasselbalch equation relates the pH of a solution containing a mixture of the two components to the acid dissociation constant , K a of the acid ...
In chemistry, biochemistry, and pharmacology, a dissociation constant (K D) is a specific type of equilibrium constant that measures the propensity of a larger object to separate (dissociate) reversibly into smaller components, as when a complex falls apart into its component molecules, or when a salt splits up into its component ions.
The stepwise constant, K, for the formation of the same complex from ML and L is given by ML + L ⇌ ML 2; [ML 2] = K[ML][L] = Kβ 11 [M][L] 2. It follows that β 12 = Kβ 11. A cumulative constant can always be expressed as the product of stepwise constants. There is no agreed notation for stepwise constants, though a symbol such as K L
See Amino acid for the pK a values of all amino acid side chains inferred in such a way. There are also numerous experimental studies that have yielded such values, for example by use of NMR spectroscopy. The table below lists the model pK a values that are often used in a protein pK a calculation, and contains a third column based on protein ...
The data should have a linear relationship, the equation for which can be found by fitting the data using the linear form of the Van 't Hoff equation ln K e q = − Δ r H ⊖ R T + Δ r S ⊖ R . {\displaystyle \ln K_{\mathrm {eq} }=-{\frac {\Delta _{r}H^{\ominus }}{RT}}+{\frac {\Delta _{r}S^{\ominus }}{R}}.}
A plot of the common logarithm of the reaction rate constant k versus the logarithm of the ionization constant K a for a series of acids (for example a group of substituted phenols or carboxylic acids) gives a straight line with slope α and intercept C. The Brønsted equation is a free-energy relationship.
The absorption rate constant K a is a value used in pharmacokinetics to describe the rate at which a drug enters into the system. It is expressed in units of time −1. [1] The K a is related to the absorption half-life (t 1/2a) per the following equation: K a = ln(2) / t 1/2a. [1] K a values can typically only be found in research articles. [2]