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The concentration of sites is given by dividing the total number of sites (S 0) covering the whole surface by the area of the adsorbent (a): [ S 0 ] = S 0 / a . {\displaystyle [S_{0}]=S_{0}/a.} We can then calculate the concentration of all sites by summing the concentration of free sites [ S ] and occupied sites:
Charge carrier density, also known as carrier concentration, denotes the number of charge carriers per volume. In SI units, it is measured in m −3. As with any density, in principle it can depend on position. However, usually carrier concentration is given as a single number, and represents the average carrier density over the whole material.
At 298 K, 1 pH unit is approximately equal to 59 mV. [2] When the electrode is calibrated with solutions of known concentration, by means of a strong acid–strong base titration, for example, a modified Nernst equation is assumed. = + [] where s is an empirical slope factor.
The Henderson–Hasselbalch equation can be used to model these equilibria. It is important to maintain this pH of 7.4 to ensure enzymes are able to work optimally. [10] Life threatening Acidosis (a low blood pH resulting in nausea, headaches, and even coma, and convulsions) is due to a lack of functioning of enzymes at a low pH. [10]
Variable pathlength absorption spectroscopy uses a determined slope to calculate concentration. As stated above this is a product of the molar absorptivity and the concentration. Since the actual absorbance value is taken at many data points at equal intervals, background subtraction is generally unnecessary.
The absorbance of a material that has only one absorbing species also depends on the pathlength and the concentration of the species, according to the Beer–Lambert law =, where ε is the molar absorption coefficient of that material; c is the molar concentration of those species; ℓ is the path length.
[10]: 280–4 Hence, a single experiment can be used to measure the logarithms of the partition coefficient (log P) giving the distribution of molecules that are primarily neutral in charge, as well as the distribution coefficient (log D) of all forms of the molecule over a pH range, e.g., between 2 and 12.
An observable that is proportional to complex formation (such as absorption signal or enzymatic activity) is plotted against the mole fractions of these two components. χ A is the mole fraction of compound A and P is the physical property being measured to understand complex formation. This property is most oftentimes UV absorbance. [2]