Asteroid impact enriches certain elements in seawater

Asteroid strikes upset the environment and provide clues via the elements they leave behind. Now, University of Tsukuba researchers have linked elements that are enriched in the Cretaceous–Paleogene (KPg) boundary clays ...

Scientists use light to convert fatty acids into alkanes

Researchers led by Prof. Wang Feng at the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences have reported that photocatalytic decarboxylation is an efficient alternate pathway for converting biomass-derived ...

Electrocatalyst exhibits superb water splitting activity

A recent study, affiliated with South Korea's Ulsan National Institute of Science and Technology (UNIST) has reported a phosphate-based electrocatalyst of Fe3Co(PO4)4/reduced-graphene-oxide (rGO) (1) for OER, which is predicted ...

Eliminating viruses in our food with cranberries and citrus fruit

Fresh produce is a major vehicle for noroviruses, a group of viruses that are the most common cause of gastroenteritis in developed countries. However, the viruses are quite resistant to cold pasteurization treatments such ...

Atomic structures mapped in measles, mumps, flu and RSV

Northwestern University researchers have, for the first time, determined the 3-D atomic structure of a key complex in paramyxoviruses, a family of viruses that includes measles, mumps, human parainfluenza and respiratory ...

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