Content
In the field of chemistry, they are generally called bases (or hydroxides) at substances that, when dissolved in water, release hydroxyl ions (OH–) and acids to which they are capable of releasing protons (H+).
The concept of bases and acids it has been modified a bit over time. It was Arrhenius who drew up the first definition, his theory had some limitations, since certain substances such as ammonia behave like bases without having the hydroxyl ion in their molecule. In addition, Arrhenius only considered the aqueous medium, but acid-base reactions also occur in other media. dissolution not aqueous.
Almost forty years later, around 1923, Brönsted and Lowry formulated another theory by stating that acids and bases act as conjugated pairs, in such a way that acid is that substance capable of providing protons and the base is that capable of taking them. Even this theory was not completely complete, since there are several substances that have acidic properties without having atoms of ionizable hydrogen in its molecule.
That is why as an additional part of his theory about the covalent bond interatomic, Lewis pointed out that acid is all that substance that can accept a pair of electrons to form a coordinated covalent bond (dative), while any substance capable of giving up said electronic pair is a base.
According to their tendency to dissociation into ions, acids and bases are classified into strong and weak. Acids decrease pH of solutions, bases or alkalis raise it. Strong acids are often corrosive, some substances dissolve better in media that have been slightly acidified or alkalized.
Examples of acids
Some well known acids, by way of example:
- sulfuric acid (H2SW4) - it is a strong acid with many uses, especially in heavy industry, very corrosive and irritating; When diluted, it releases a lot of heat, so it must be handled (like other strong acids) with great care. Strongly oxidizing.
- hydrochloric acid (HCl) - although it is a strong acid, it is present in the human body, specifically in the stomach, where it plays an important role in the digestive process. Its excess generates heartburn.
- phosphoric acid (H3PO3) - this acid is a common ingredient in carbonated drinks. The regular consumption of such drinks is discouraged due to the negative impact of this acid on calcium metabolism, which affects bones and teeth above all.
- nitric acid (HNO3) - recognized strong acid, used to make explosives and nitrogen fertilizers, among other uses.
- perchloric acid (HClO4) - another strong acid that is liquid at room temperature, it is one of the most oxidizing.
- hydrogen sulfide (H2S) - is a gaseous substance with a strong and unpleasant odor, toxic in high concentrations, it has numerous industrial applications.
- ribonucleic acid - It is a central component of ribosomes, essential for the global process of protein synthesis to be completed from deoxyribonucleic acid, closely related to it.
- acetylsalicylic acid - It is a very important organic acid, with analgesic and anti-inflammatory properties; It is the basis of aspirin.
- lactic acid - comes from the breakdown of glucose during anaerobic exercise of high intensity and short duration. Under normal conditions, this lactic acid is reused, but if it accumulates, it causes damage to muscle fibers, especially in the form of cramps.
- allylic acid - It is an acid present in vegetables such as garlic or onion, derived from a precursor also present in such species, allicin. It is germicidal and antioxidant.
- Retinoic acid - applied topically, inhibits keratinization, is used in creams against acne and skin aging. It should be used under medical supervision.
- butyric acid - final product of the fermentation of certain carbohydrates carried out by microorganisms in the rumen; it is usually part of animal fats in small amounts.
- propionic acid - food preservative, it is used in order to prevent fungal and bacterial spoilage of bakery products and others.
- benzoic acid - it is used as a preservative added to different products (mayonnaise, canned goods), often in the form of salt (sodium benzoate)
- acetic acid - Food preservative widely used in the home, base for vinaigrettes and pickles. It is the majority component of vinegar.
- acidhydroiodic
- succinic acid
- hydrobromic acid
- citric acid
- acidoxalic
See also in: Examples of Acids
Examples of bases
Now, some bases are listed (those of metals are generically known as hydroxides):
- sodium hydroxide (caustic soda)
- magnesium hydroxide (milk of magnesia)
- calcium hydroxide(lime)
- potassium hydroxide
- barium hydroxide
- iron hydroxide
- Ammonia
- Soap
- Detergent
- Quinine
- Aniline
- Guanine
- Pyrimidine
- Cytosine
- Adenine
- zinc hydroxide
- copper hydroxide
- zirconium hydroxide
- titanium hydroxide
- aluminum hydroxide(antacid)
See more at: Examples of Chemical Bases
