- Alternate uses: see Ph
pH (potential (of) hydrogen) is a measure of the concentration of hydrogen ions (H+) in a solution and, therefore, its acidity or alkalinity. The concept was introduced by S.P.L. Sørensen in 1909. The p stands for the German potenz, meaning power or concentration, and the H for the hydrogen ion (H+).
In layman's terms , the "pH" value is an approximate number between 0 and 14 that indicates whether a solution is acidic (pH < 7), neutral (pH = 7), or basic (pH > 7) .
1 Definition
The formula for calculating pH is:
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[H+] indicates the activity of H+ ions (also written [H3O+], the equivalent hydronium ions), measured in moles per litre (also known as molarity). In dilute solutions (like river or tap water) the activity is approx. equal to the concentration of the H+-ion.
In aqueous solution at standard temperature and pressure, a pH of 7 indicates neutrality (e.g. pure water) because waterDrinking water This article focuses on water as we experience it every day. The water (molecule) article describes water from a scientific and technical perspective. Water is an abundant substance on Earth. It exists in many forms, such as sea, rain, and naturally dissociates into H+ and OH- ions with equal concentrations of 1×10-7 M. A lower pH number (for example pH 3) indicates increasing strength of acidity, and a higher pH number (for example pH 11) indicates increasing strength of alkalinity.
Most substances have a pH in the range 0 to 14, although extremely acidic or basic substances may have pH < 0, or pH > 14.
In nonaqueous solutions or non-STP conditions, the pH of neutrality may not be 7. Instead it is related to the dissociation constantIn chemistry and biochemistry the dissociation constant abbreviated K is a measure of the extent to which a dissociation reaction :AB ↔ A + B proceeds at equilibrium. It is given quantitatively by the expression K [A]×[B]×[AB]-1 Where [A], [B], and [ for the specific solventA solvent is a liquid that dissolves a solute. The solvent is the component of a solution that is present in greater amount. See solution. Perhaps the most common solvent in everyday life is water. Many other solvents are organic compounds, such as benzen used.
Some common pH values
| Substance | pH
|
| BatteryIn science and technology, a battery is a device that stores energy and makes it available in an electrical form. Although such storage in an electrostatic form is practical in some specialized uses, batteries usually consist of electrochemical devices su acid | <1.0
|
| Gastric acidGastric acid is the main secretion of the stomach, characterised by HO, hydrochloric acid and several enzymes (mainly pepsinogen). Physiology Gastic acid is produced by the parietal cell (wall cell) of the gastric mucosa. The pH of gastric acid is 2-3, th | 2.0
|
| LemonLemons are the citrus fruit from the tree Citrus limon''. They are cultivated primarily for their juice, though the pulp and rind are also used, primarily in cooking. Lemon juice is about 5% citric acid, which gives lemons a sour taste. The lemon was unkn juice | 2.4
|
| ColaIn botany and slang, colas are the flowers of the cannabis plant. A cola is a sweet carbonated drink, usually with caramel flavoring and containing caffeine. The flavor of the drink sometimes comes from a mixture of vanilla, cinnamon, and citrus flavoring | 2.5
|
| VinegarVinegar (from Old French vinaigre "sour wine") is a sour liquid made from the oxidation of ethanol in wine, cider, beer, or the like. Vinegar is typically three to five percent by volume acetic acid, and natural vinegars also contain smaller amounts of ta | 2.9
|
| Orange or apple juice | 3.5
|
| Beer | 4.5
|
| Coffee | 5.0
|
| Tea | 5.5
|
| Acid rain | < 5.6
|
| Human Saliva in Cancer patients | 4.5-5.7
|
| Milk | 6.5
|
| Pure water | 7.0
|
| Human Saliva | 6.5-7.4
|
| Blood | 7.34 - 7.45
|
| Sea water | 8.0
|
| Hand soap | 9.0 - 10.0
|
| Household ammonia | 11.5
|
| Bleach | 12.5
|
| Household lye | 13.5
|
