Pediatrics

Probiotic may help treat colic in infants

Probiotics—or "good bacteria"—have been used to treat infant colic with varying success. In a new trial published in the journal Alimentary Pharmacology & Therapeutics, investigators have shown that drops containing a ...

Diseases, Conditions, Syndromes

Got chronic heartburn? Easy does it during the Thanksgiving feast

(HealthDay)—The turkey, stuffing, cranberries, green bean casserole and mashed potatoes on the Thanksgiving table may look tempting, but if you have gastroesophageal reflux disease (GERD) you should proceed with caution, ...

Immunology

Simulating amino acid starvation may improve dengue vaccines

Eating a low-calorie diet can help you live longer and prevent age-related diseases—and even improve the immune system's function. A new study finds that, in mice, a compound used in herbal medicine can give a similar immune ...

Medical research

Researchers report possible biomarker for pain in spinal fluid

Pain: we all experience it, but there's no objective way to measure it. Sure, you can nominate what it feels like on the 10-point pain scale used by doctors; but one man's pain may be another woman's discomfort.

Neuroscience

High-fat maternal diet can cause brain damage in the unborn child

A research team at MedUni Vienna's Center for Brain Research has found that high-fat maternal diets can cause life-long changes in the brains of the unborn offspring. When a pregnant woman consumes a diet high in polyunsaturated ...

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