News tagged with acid

Possible risk of folic acid overexposure

A new study has shown that synthetic folic acid, the form taken in folic acid supplements we can buy over the counter, is not processed by the body in the same way as natural folates, the form found in green vegetables.

Jul 25, 2014
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Antioxidant biomaterial promotes healing

When a foreign material like a medical device or surgical implant is put inside the human body, the body always responds. According to Northwestern University's Guillermo Ameer, most of the time, that response can be negative ...

Jul 24, 2014
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Researchers find new mechanism for neurodegeneration

A research team led by Jackson Laboratory Professor and Howard Hughes Investigator Susan Ackerman, Ph.D., have pinpointed a surprising mechanism behind neurodegeneration in mice, one that involves a defect in a key component ...

Jul 24, 2014
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Mysterious esophagus disease is autoimmune after all

(Medical Xpress)—Achalasia is a rare disease – it affects 1 in 100,000 people – characterized by a loss of nerve cells in the esophageal wall. While its cause remains unknown, a new study by a team of researchers at ...

Jul 22, 2014
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Healing the heart with fat

Too much dietary fat is bad for the heart, but the right kind of fat keeps the heart healthy, according to a paper published in The Journal of Experimental Medicine.

Jul 21, 2014
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Improved imaging agent pinpoints hostile cancer

Positron emission tomography (PET) could prove to be a better imaging procedure than magnetic resonance imaging (MRI) in the detection of glioblastoma, the most aggressive type of primary brain tumour.

Jul 08, 2014
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Acid

An acid (from the Latin acidus/acēre meaning sour) is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red. Chemicals or substances having the property of an acid are said to be acidic.

Common examples of acids include acetic acid (in vinegar), sulfuric acid (used in car batteries), and tartaric acid (used in baking). As these three examples show, acids can be solutions, liquids, or solids. Gases such as hydrogen chloride can be acids as well. Strong acids and some concentrated weak acids are corrosive, but there are exceptions such as carboranes and boric acid.

There are three common definitions for acids: the Arrhenius definition, the Brønsted-Lowry definition, and the Lewis definition. The Arrhenius definition states that acids are substances which increase the concentration of hydronium ions (H3O+) in solution. The Brønsted-Lowry definition is an expansion: an acid is a substance which can act as a proton donor. Most acids encountered in everyday life are aqueous solutions, or can be dissolved in water, and these two definitions are most relevant. The reason why pHs of acids are less than 7 is that the concentration of hydronium ions is greater than 10−7 moles per liter. Since pH is defined as the negative logarithm of the concentration of hydronium ions, acids thus have pHs of less than 7. By the Brønsted-Lowry definition, any compound which can easily be deprotonated can be considered an acid. Examples include alcohols and amines which contain O-H or N-H fragments.

In chemistry, the Lewis definition of acidity is frequently encountered. Lewis acids are electron-pair acceptors. Examples of Lewis acids include all metal cations, and electron-deficient molecules such as boron trifluoride and aluminium trichloride. Hydronium ions are acids according to all three definitions. Interestingly, although alcohols and amines can be Brønsted-Lowry acids as mentioned above, they can also function as Lewis bases due to the lone pairs of electrons on their oxygen and nitrogen atoms.

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