New tRNA promotes synthesis of streptomyces antibiotics

A research team led by Prof. Liu Guangxiu from the Northwest Institute of Eco-Environment and Resources of the Chinese Academy of Sciences (CAS) has isolated a fast-growing desert streptomycete from an extreme environment ...

New method can remove dyes from wastewater

North Carolina State University researchers have demonstrated that a synthetic polymer can remove certain dyes from water, and that the polymer can be recovered and reused. The findings offer a new potential method for cleaning ...

Scientists identify mechanism crucial for COVID-19 virus replication

A team led by UT Southwestern researchers has identified how SARS-CoV-2, the virus that causes COVID-19, builds a structure called the RNA cap that's critical for successful viral replication. The finding, published in Nature, ...

How calcium ions get into the cellular power stations of plants

Calcium is a very special nutrient. In the cells of most living beings calcium ions function as so-called second messengers to transmit important signals. The same applies equally to animal, plant and fungal cells. Through ...

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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