# What is pH?

rupadhye | College Teacher | (Level 1) eNoter

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In CHEMISTRY, pH is a measure of the CIDITY or basicity or alkalinity a solution. Pure water is said to be neutral, with a pH close to 7.0 at 25 deg C.Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are said to be basic or alkaline.

william1941 | College Teacher | (Level 3) Valedictorian

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The term pH is used to refer to the hydrogen ion concentration of a solution. Acidic environments are rich in hydrogen ions while basic environments have a lesser concentration of hydrogen ions. The pH scale is calculated as the negative logarithm of the hydrogen ion concentration. As an example water has a pH of 7 as the hydrogen ion concentration is 10^ (-7). pH can range from 0 to 14 with 0 being the most acidic and 14 being the most alkaline. As pH values lie on a logarithmic scale a change of 1 equates to a tenfold change in the hydrogen ion concentration.

andyluv | Student, Grade 11 | (Level 1) Honors

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A measure of the acidity or alkalinity of a solution, numerically equal to 7 for neutral solutions, increasing with increasing alkalinity and decreasing with increasing acidity. The pH scale commonly in use ranges from 0 to 14.

It is defined as the negative common logarithm of the concentration of hydrogen ions [H+] in moles/litre: pH = -log10 [H+]. The letters of its name are derived from the absolute value of the power (p) of the hydrogen ion concentration (H). The strongest acid solution has about 1 mole/litre of H+ (and about 10-14 of OH-), for a pH of 1. The strongest basic solution has about 10-14 moles/litre of H+ (and about 1 of OH-), for a pH of 14. A neutral solution has about 10-7 moles/litre of both H+ and OH-, for a pH of 7. The pH value, measured by a pH meter, titration, or indicator (e.g., litmus) strips, helps inform chemists of the nature, composition, or extent of reaction of substances, biologists of the composition and environment of organisms or their parts or fluids, physicians of the functioning of bodily systems, and agronomists of the suitability of soils for crops and any treatments needed.

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juliet926 | Student, Grade 10 | (Level 1) Salutatorian

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The pH can be 1-4 in acidic solutions such as concentrated nitric acid, neutral at about pH 7 and alkaline at pH 8-14.

roy01 | College Teacher | eNotes Newbie

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pH is a measure of the acidity or basicity of a solution. It is defined as the cologarithm of the activity of dissolved hydrogen ions (H+). ... Unit to measure the hydrogen-ion concentration. It is measured on a scale from 0 to 14 with 7 the neutral point.

The pH of a solution is a measure of the molar concentration of hydrogen ions in the solution and as such is a measure of the acidity or basicity of the solution. The letters pH stand for "power of hydrogen"

lit24 | College Teacher | (Level 3) Valedictorian

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pH stands for potential of Hydrogen. It is the measure of the acidity or basicity of a solution.

It is defined as the logarithm of the reciprocal  of hydrogen-ion concentration in gram atoms per liter on  a scale from 0 to 14 of the acidity or alkalinity of a solution where 7 is neutral, and greater than 7 is more basic and less than 7 is more acidic.

The concept of pH was first introduced by the Danish chemist Soren Peder Lauritz Sorensen at the Carlsberg Laboratory in 1909.