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The Acid are an electronic music quartet consisting of British DJ and record producer Adam Freeland; Californian producer, composer, and professor of music technology Steve Nalepa; American singer/songwriter Jens Kuross; and Los Angeles–based Australian artist RY X.
- 2013–present
Play ∴ The Acid ∴ and discover followers on SoundCloud | Stream tracks, albums, playlists on desktop and mobile.
4. Juli 2022 · Acid–base reactions require both an acid and a base. In Brønsted–Lowry terms, an acid is a substance that can donate a proton (H +), and a base is a substance that can accept a proton. All acid–base reactions contain two acid–base pairs: the reactants and the products.
Acids are molecular compounds that release hydrogen ions. A binary acid consists of hydrogen and one other element. Oxyacids contain hydrogen, oxygen, and one other element. The name of the acid is based on the anion attached to the hydrogen.
- Overview
- Introduction
- Autoionization of water
- Acids and bases
- The pH scale
- Buffers
Acidity and basicity, proton concentration, the pH scale, and buffers.
Even if you’ve never set foot in a chemistry lab, chances are you know a thing or two about acids and bases. For instance, have you drunk orange juice or cola? If so, you know some common acidic solutions. And if you’ve ever used baking soda, or even egg whites, in your cooking, then you’re familiar with some bases as well1 .
You may have noticed that acidic things tend to taste sour, or that some basic things, like soap or bleach, tend to be slippery. But what does it actually mean for something to be acidic or basic? To give you the short answer:
•An acidic solution has a high concentration of hydrogen ions (H+ ), greater than that of pure water.
•A basic solution has a low H+ concentration, less than that of pure water.
Hydrogen ions are spontaneously generated in pure water by the dissociation (ionization) of a small percentage of water molecules. This process is called the autoionization of water:
H2 O (l) ⇌ H+ (aq) + OH− (aq)
The letters in parentheses just mean that the water is liquid (l), and that the ions are in aqueous (water-based) solution (aq).
As shown in the equation, dissociation makes equal numbers of hydrogen (H+ ) ions and hydroxide (OH− ) ions. While the hydroxide ions can float around in solution as hydroxide ions, the hydrogen ions are transferred directly to a neighboring water molecule to form hydronium ions (H3 O+ ). So, there aren't really H+ ions floating around freely in water. However, scientists still refer to hydrogen ions and their concentration as if they were free-floating, not in hydronium form – this is just a shorthand we use by convention.
So, how many water molecules in a pitcher of water will actually dissociate? The concentration of hydrogen ions produced by dissociation in pure water is 1 × 10−7 M (moles per liter of water).
[What is this "mole" thing?]
Solutions are classified as acidic or basic based on their hydrogen ion concentration relative to pure water. Acidic solutions have a higher H+ concentration than water (greater than 1 × 10−7 M), while basic (alkaline) solutions have a lower H+ concentration (less than 1 × 10−7 M). Typically, the hydrogen ion concentration of a solution is expressed in terms of pH. pH is calculated as the negative log of a solution’s hydrogen ion concentration:
pH =−log10 [H + ]
The square brackets around the H+ just mean that we are referring to its concentration. If you plug the hydrogen ion concentration of water (1 × 10−7 M) into this equation, you’ll get a value of 7.0, also known as neutral pH. In the human body, both blood and the cytosol (watery goo) inside of cells have pH values close to neutral.
H+ concentration shifts away from neutral when an acid or base is added to an aqueous (water-based) solution. For our purposes, an acid is a substance that increases the concentration of hydrogen ions (H+ ) in a solution, usually by donating one of its hydrogen atoms through dissociation. A base, in contrast, raises pH by providing hydroxide (OH− ) or another ion or molecule that scoops up hydrogen ions and removes them from solution. (This is a simplified definition of acids and bases that works well for thinking about biology. You may want to visit the chemistry section to see other acid-base definitions.)
The pH scale is used to rank solutions in terms of acidity or basicity (alkalinity). Since the scale is based on pH values, it is logarithmic, meaning that a change of 1 pH unit corresponds to a ten-fold change in H+ ion concentration. The pH scale is often said to range from 0 to 14, and most solutions do fall within this range, although it’s possible to get a pH below 0 or above 14. Anything below 7.0 is acidic, and anything above 7.0 is alkaline, or basic.
The pH inside human cells (6.8) and the pH of blood (7.4) are both very close to neutral. Extreme pH values, either above or below 7.0, are usually considered unfavorable for life. However, the environment inside your stomach is highly acidic, with a pH of 1 to 2. How does the stomach get around this problem? The answer: disposable cells! Stomach cells, particularly those that come in direct contact with stomach acid and food, are constantly dying and being replaced by new ones. In fact, the lining of the human stomach is completely replaced about every seven to ten days.
Most organisms, including humans, need to maintain pH within a fairly narrow range in order to survive. For instance, human blood needs to keep its pH right around 7.4, and avoid shifting significantly higher or lower – even if acidic or basic substances enter or leave the bloodstream.
Buffers, solutions that can resist changes in pH, are key to maintaining stable H+ ion concentrations in biological systems. When there are too many H+ ions, a buffer will absorb some of them, bringing pH back up; and when there are too few, a buffer will donate some of its own H+ ions to reduce the pH. Buffers typically consist of an acid-base pair, with the acid and base differing by the presence or absence of a proton (a conjugate acid-base pair).
For instance, one of the buffers that maintain the pH of human blood involves carbonic acid (H2 CO3 ) and its conjugate base, the bicarbonate ion (HCO3 − ). Carbonic acid is formed when carbon dioxide enters the bloodstream and combines with water, and it is the main form in which carbon dioxide travels in the blood between the muscles (where it’s generated) and the lungs (where it’s converted back into water and CO2 , which is released as a waste product).
If too many H+ ions build up, the equation above will be pushed to the right, and bicarbonate ions will absorb the H+ to form carbonic acid. Similarly, if H+ concentrations drop too low, the equation will be pulled the left and carbonic acid will turn into bicarbonate, donating H+ ions to the solution. Without this buffer system, the body’s pH would fluctuate enough to put survival in jeopardy.
14. Feb. 2023 · In chemistry, an acid is a chemical species that donates hydrogen ions or protons or accepts an electron pair. Acids react with bases and some metals via a neutralization reaction that forms a salt. They have a pH less than 7 and taste sour. The word acid comes from the Latin word acidus, which means “sour.”
What is an acid, as defined in chemistry? What are the examples of mineral acids? What are the examples of nonaqueous acids? What are the examples of organic compounds that are acids? What is the difference between an acid and a base?
