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What Is the pH Scale?
Measurement of Acidity & Alkalinity
from Science Prof Online
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What Is an Acid?
An acid is any ionic compound that releases hydrogen ions (H+) in solution. Weak acids have a sour taste. Strong acids are highly corrosive. The more hydrogen ions in the solution, the more acidic it is.
What Is a Base?
Bases, also called alkaline substances, are ionic compounds that release hydroxyl ions (OH-) in solution. Weak bases have a bitter taste (opposed to sour taste of acids and sweetness of aldehydes and ketones), are slimy to the touch. The more hydroxyl ions in solution, the more alkaline it is.
Measurements of pH
Acidity or alkalinity of a solution is measured by concentration of hydrogen ions (H+) versus hydroxyl ions (OH-) and is expressed as pH level, a exponential scale that ranges from 0 (very acidic) to 14 (very basic).
Article Summary: The pH scale is a measurement of the acidity or alkalinity of a solution. To understand the scale, it is important to first understand what acids and bases are.
Acids, Bases, Buffers, and the pH Scale
Because the scale is logarithmic, a change of just one unit represents a tenfold change in H+ concentration. When the concentration of hydrogen ions (H+) equals the concentration of hydroxyl ions (OH-) a solution is neutral.
Salts and pH Buffering
Salts are inorganic molecules can act as buffers to reduce fluctuations in pH by releasing cations and anions other than H+ and OH- in solution. An example of a salt buffer is the antacid calcium carbonate (CaCO3). Carbonate reacts with a free hydrogen ion (H+), forming bicarbonate. Then bicarbonate reacts with a free hydrogen ions to create carbonic acid (H2CO3), which then can dissociate (break down further) into water (H2O) and carbon dioxide (CO2). During this process, free hydrogen ions are locked up, which prevents the pH from lowering.
This article originally appeared on Suite101 online magazine.
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