Search results
Results From The WOW.Com Content Network
log 10 β values between about 2 and 11 can be measured directly by potentiometric titration using a glass electrode. This enormous range of stability constant values (ca. 100 to 10 11) is possible because of the logarithmic response of the electrode. The limitations arise because the Nernst equation breaks down at very low or very high pH.
In this case, K eq can be defined as ratio of B to C rather than the equilibrium constant. When B / C > 1, B is the favored product, and the data on the Van 't Hoff plot will be in the positive region. When B / C < 1, C is the favored product, and the data on the Van 't Hoff plot will be in the negative region.
The apparent dimension of this K value is concentration 1−p−q; this may be written as M (1−p−q) or mM (1−p−q), where the symbol M signifies a molar concentration (1M = 1 mol dm −3). The apparent dimension of a dissociation constant is the reciprocal of the apparent dimension of the corresponding association constant , and vice versa .
It is equivalent to the slope of the Hammett plot. Information on the reaction and the associated mechanism can be obtained based on the value obtained for ρ. If the value of: ρ>1, the reaction is more sensitive to substituents than benzoic acid and negative charge is built during the reaction (or positive charge is lost).
If it is measured at a series of different ionic strengths, the value can be extrapolated to zero ionic strength. [12] The concentration quotient obtained in this manner is known, paradoxically, as a thermodynamic equilibrium constant.
A mathematical constant is a key number whose value is fixed by an unambiguous definition, often referred to by a symbol (e.g., an alphabet letter), or by mathematicians' names to facilitate using it across multiple mathematical problems. [1]
A simple example is provided by the effect of replacing the hydrogen atoms in acetic acid by the more electronegative chlorine atom. The electron-withdrawing effect of the substituent makes ionisation easier, so successive pK a values decrease in the series 4.7, 2.8, 1.4, and 0.7 when 0, 1, 2, or 3 chlorine atoms are present. [49]
The value of each log D is then determined as the logarithm of a ratio—of the sum of the experimentally measured concentrations of the solute's various forms in one solvent, to the sum of such concentrations of its forms in the other solvent; it can be expressed as [10]: 275–8