Engineering

Wearable sweat sensor detects gout-causing compounds

There are numerous things to dislike about going to the doctor: Paying a copay, sitting in the waiting room, out-of-date magazines, sick people coughing without covering their mouths. For many, though, the worst thing about ...

Energy & Green Tech

Li-ion batteries: Science 'directly into your hand'

They are omnipresent and essential to navigating modern life. Small, light, rechargeable: lithium ion batteries have revolutionised our world in less than three decades.

Engineering

One-dimensional objects morph into new dimensions

A line is the shortest distance between two points, but "A-line," a 4-D printing system developed at Carnegie Mellon University, takes a more circuitous route. One-dimensional, "line"-shaped plastic structures produced with ...

Energy & Green Tech

Algae and bacteria team up to increase hydrogen production

In line with the fight against climate change and the search for a sustainable future, there is the idea of a future society based on hydrogen used as a fuel. This biofuel of the future could be what cars and engines run ...

Machine learning & AI

Artificial intelligence to predict protein structure

Proteins are biological high-performance machines. They can be found in every cell and play an important role in human blood coagulation or as main constituents of hairs or muscles. The function of these molecular tools is ...

Machine learning & AI

Machine learning for damaging mutations prediction

Next-generation sequencing technology has ushered in a new era in medicine, making it easier to identify a sequence of nucleotides in DNA or a sequence of amino acids in the proteins of a specific individual and use this ...

Engineering

Rocket fuel and 3-D printing

James Cook University scientists in Australia are using 3-D printing to create fuels for rockets, and using tailor-made rocket motors they've built to test the fuels.

Energy & Green Tech

Low-cost catalyst boosts hydrogen production from water

A future powered by carbon-free fuel depends on our ability to harness and store energy from renewable but intermittent sources, such as solar and wind. Now, a new catalyst developed at University of Toronto Engineering gives ...

Engineering

TINY cancer detection device proves effective in Uganda testing

Its name is an acronym used to convey its size, but researchers at Cornell Engineering and Weill Cornell Medicine are hoping their hand-held cancer detection device's impact in the developing world is anything but small.

Engineering

A glucose testing patch that doesn't require pricking the skin

A team of researchers from Tsinghua University working with People's Liberation Army Air Force General Hospital, both in China, has developed a two-stage patch that can be used to test glucose levels. In their paper published ...

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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