Electronics & Semiconductors

New wearable sensor sets record for solar power efficiency

Sweat, like blood, can tell us a lot about a person's health. And conveniently, it's a lot less invasive to collect. This is the premise behind the wearable sweat sensors developed by Wei Gao, assistant professor of medical ...

Energy & Green Tech

Eight EU countries oppose bloc's car emissions limits

Eight EU member states including France, Italy and Poland urged Brussels to scrap its planned vehicle emissions limits, warning they risked hurting investment in a document seen by AFP Monday.

Energy & Green Tech

Unlocking the power of photosynthesis for clean energy production

As the world faces an increasing demand for clean and sustainable energy sources, scientists are turning to the power of photosynthesis for inspiration. With the goal of developing new, environmentally friendly techniques ...

Engineering

Electronic nose determines the quality of wine

An electronic nose consists of some sensors, a signal processing system and an analysis system. "The e-nose can identify substances using a method similar to the human sense of smell. The use of AI is increasing the potential ...

Energy & Green Tech

Lithium recovery can supplement power generation and heat supply

Geothermal technology not only enables sustainable supply of electricity and heat, but also regional lithium extraction. Researchers from Karlsruhe Institute of Technology (KIT) and EnBW have produced a lithium-ion sieve ...

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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