News tagged with acid

Changing cows' diet could help tackle heart disease

Adding oilseed to a cow's diet can significantly reduce the harmful saturated fat found in its milk without compromising the white stuff's nutritional benefits, according to research by the University of ...

9 hours ago
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Researchers examine metabolism in defective cells

University of Alberta researchers are taking a closer look at how two metabolic pathways interact to increase the lifespan of cells with mitochondrial defects. Magnus Friis is the lead author of the study, which was published ...

Apr 11, 2014
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Switching brain cells with less light

Networked nerve cells are the control center of organisms. In a nematode, 300 nerve cells are sufficient to initiate complex behavior. To understand the properties of the networks, re-searchers switch cells ...

Apr 01, 2014
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Can vitamin A turn back the clock on breast cancer?

A derivative of vitamin A, known as retinoic acid, found abundantly in sweet potato and carrots, helps turn pre-cancer cells back to normal healthy breast cells, according to research published this month in the International Jo ...

Mar 31, 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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