Could young blood hold secrets to longer, healthier life?

In what sounds like a scene from a science fiction movie, researchers in 2005 stitched together old and young mice so they shared a circulatory system. Youthful blood seemingly rejuvenated many tissues of the elderly rodents, ...

X marks the spot: recombination in structurally distinct chromosomes

Two years ago, scientists from the Stowers Institute for Medical Research reported the 3-D structure of the synaptonemal complex in the fruit fly Drosophila melanogaster. This large protein complex is a critical player in ...

A rat's brain, on and off methamphetamine

Drug addiction is a vicious cycle of reward and withdrawal. Chronic users often relapse because of the unpleasant physical and psychological symptoms they experience when they stop taking the drug. Now, researchers report ...

Wily tuberculosis bacteria can vary its diet to infect you longer

Worldwide, approximately one in four people is infected by Mycobacterium tuberculosis and while overall New Zealand has relatively low rates of TB, Māori and Pacific people are eight times more likely to be affected than ...

Method to protect carp from the harmful effects of ammonia

Veterinarians from RUDN University have developed a way to increase the resistance of carp, the most common fish in fish farms, to the harmful effects of ammonia, which is found in almost all water bodies. The researchers ...

Shipment tracking for 'fat parcels' in the body

Without fat, nothing works in the body: Fats serve as energy suppliers and important building blocks, including for the envelopes of living cells. Numerous diseases are related to disorders in fat metabolism such as obesity ...

page 1 from 23

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.

This text uses material from Wikipedia, licensed under CC BY-SA