Noun interpretation

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Hydrogen ion concentration index (English hydrogen

ion

Concentration, French potential

D' hydrogene) refers to the ratio of the total number of hydrogen ions to the total number of substances in the solution. Its numerical value is commonly known as "pH (British pronunciation: /pi'et∫/, /pi:'eit∫/, French pronunciation /pea∫/, because pH is the abbreviation of French, it is recommended to pronounce it in French)". express

Meaning of pH value of solution

The basis for judging the acidity, neutrality or alkalinity of a solution is the relative concentration of [H+] and [OH-]. Solution [h+] > at any temperature; When [OH-] is acidic, when [H+]=[OH-], [H+] is neutral.

At standard temperature (25℃) and pressure, an aqueous solution with pH=7 (such as pure water) is neutral, because the product of the concentrations of hydrogen ions and hydroxyl ions naturally ionized by water at standard temperature and pressure (the ion product constant of water) is always 1× 10- 14, and the concentrations of both ions are 60. A small pH value means that the concentration of H+ is greater than that of OH-, so the solution is acidic, while a large pH value means that the concentration of H+ is less than that of OH-, so the solution is alkaline. Therefore, the smaller the pH value, the stronger the acidity of the solution. The greater the pH value, the stronger the alkalinity of the solution.

Generally, the pH value is a number between 0 and 14. When the pH value is 7, the solution is alkaline; when the pH value is 7, the solution is neutral. However, under the condition of non-aqueous solution or non-standard temperature and pressure, pH=7 does not necessarily mean that the solution is neutral, so it is necessary to calculate the ionization constant of the solvent under this condition to determine the neutral value. For example, at the temperature of 373K( 100℃), pH=6 is a neutral solution.

The value of acidity or alkalinity of a solution, that is, the negative value of the common logarithm of the concentration of hydrogen ions contained.