Medical research

The fluid that feeds tumor cells

Before being tested in animals or humans, most cancer drugs are evaluated in tumor cells grown in a lab dish. However, in recent years, there has been a growing realization that the environment in which these cells are grown ...

Alzheimer's disease & dementia

AEDs tied to higher pneumonia risk in Alzheimer patients

(HealthDay)—Antiepileptic drug (AED) use may increase the risk for pneumonia in patients with Alzheimer disease (AD), according to a study recently published in the Journal of Alzheimer's Disease.

Medical research

Can changing the microbiome reverse lactose intolerance?

After childhood, about two-thirds of the world's human population loses the ability to digest milk. As far as we know, 100 percent of nonhuman mammals also lose this ability after weaning. The ongoing ability to digest lactose, ...

Psychology & Psychiatry

Inflammation linked to chemical imbalance in schizophrenia

A study published in Molecular Psychiatry has identified changes in inflammation-related biochemical pathways in schizophrenia that interfere with proper brain nerve cell communication. Researchers have found the first direct ...

Diabetes

Researchers identify trigger and mechanism in type 1 diabetes

Researchers at National Jewish Health have identified an elusive trigger of type 1 diabetes. A protein fragment formed in the pancreas activates the immune system's T cells, leading them to attack and destroy beta cells, ...

Health

Healthy diet helps older men maintain physical function

A person's ability to maintain independence and to physically care for themselves is an essential part of healthy aging. But few studies have examined how a person's diet may allow some aging people to maintain physical function—basic ...

Health

The skinny on beef

(HealthDay)—Beef often gets a bad rap, but is it really that bad for you?

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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.

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