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At neutral pH, the concentration of the hydroxide ion (OH −) equals that of the (solvated) hydrogen ion (H +), with a value close to 10 −7 mol L −1 at 25 °C. [76] See data page for values at other temperatures. The thermodynamic equilibrium constant is a quotient of thermodynamic activities of all products and reactants including water:
The neutral value of the pH depends on the temperature and is lower than 7 if the temperature increases above 25 °C. The pH range is commonly given as zero to 14, but a pH value can be less than 0 for very concentrated strong acids or greater than 14 for very concentrated strong bases. [2]
Polar liquids have a tendency to be more viscous than nonpolar liquids. [citation needed] For example, nonpolar hexane is much less viscous than polar water. However, molecule size is a much stronger factor on viscosity than polarity, where compounds with larger molecules are more viscous than compounds with smaller molecules.
The isoelectric point (pI, pH(I), IEP), is the pH at which a molecule carries no net electrical charge or is electrically neutral in the statistical mean. The standard nomenclature to represent the isoelectric point is pH(I). [1] However, pI is also used. [2] For brevity, this article uses pI.
Hydrophobic molecules tend to be nonpolar and, thus, prefer other neutral molecules and nonpolar solvents. Because water molecules are polar, hydrophobes do not dissolve well among them. Hydrophobic molecules in water often cluster together, forming micelles. Water on hydrophobic surfaces will exhibit a high contact angle.
Good sought to identify buffering compounds which met several criteria likely to be of value in biological research. pK a: Because most biological reactions take place near-neutral pH between 6 and 8, ideal buffers would have pK a values in this region to provide maximum buffering capacity there.
“Unlike many foods, milk is particularly hazardous because it is a nutrient-rich liquid with a neutral pH and high water activity, creating an ideal environment for bacterial growth,” Keatley ...
Bromothymol blue (also known as bromothymol sulfone phthalein and BTB) is a pH indicator. It is mostly used in applications that require measuring substances that would have a relatively neutral pH (near 7). A common use is for measuring the presence of carbonic acid in a liquid. It is typically sold in solid form as the sodium salt of the acid ...