Acid Theory
Acid (often represented by the general formula HA) is generally a chemical compound that when dissolved in water will produce a solution with a pH lower than 7. In the modern definition, an acid is a substance that can give a proton (H +) to other substances (called bases), or can accept a lone pair of bases. An acid reacts with a base in a neutralization reaction to form a salt. Examples of acids are acetic acid (found in vinegar) and sulfuric acid (used in batteries or car battery.) Acids generally taste sour, however, sour taste, especially the concentrated acid, can be dangerous and not recommended.
Various definitions of acid
The term "acid" is a translation of the term used for the same thing in European languages such as acid (English), zuur (Dutch language), or Säure (German), which is literally related to taste sour. In chemistry, the term acid has a more specific meaning. There are three commonly accepted definition of acids in chemistry, namely the definition of Arrhenius, Brønsted-Lowry, and Lewis.
• Arrhenius: According to this definition, an acid is a substance that increases the concentration of hydronium ion (H3O +) when dissolved in water. The definition was first proposed by Svante Arrhenius acids and bases are limited to substances that can dissolve in water.
• Brønsted-Lowry: According to this definition, an acid is a proton donor to the base. Acids and bases in question is called the conjugate acid-base pairs. Brønsted and Lowry independently suggested this definition, which includes substances that are insoluble in water (unlike the Arrhenius definition.)
• Lewis: According to this definition, acids are electron pair from the base receiver. The definition proposed by Gilbert N. Lewis acids which can include not contain hydrogen or protons that can be moved, such as iron (III) chloride. The Lewis definition can also be explained with molecular orbital theory. In general, an acid can receive an electron pair in its lowest unoccupied orbital (LUMO) of the highest occupied orbital (HOMO) ofbase . Thus, the HOMO from the base and the LUMO of the acids combine to form a bonding molecular orbital.
• Brønsted-Lowry: According to this definition, an acid is a proton donor to the base. Acids and bases in question is called the conjugate acid-base pairs. Brønsted and Lowry independently suggested this definition, which includes substances that are insoluble in water (unlike the Arrhenius definition.)
• Lewis: According to this definition, acids are electron pair from the base receiver. The definition proposed by Gilbert N. Lewis acids which can include not contain hydrogen or protons that can be moved, such as iron (III) chloride. The Lewis definition can also be explained with molecular orbital theory. In general, an acid can receive an electron pair in its lowest unoccupied orbital (LUMO) of the highest occupied orbital (HOMO) ofbase . Thus, the HOMO from the base and the LUMO of the acids combine to form a bonding molecular orbital.
Although it is not the most wide-ranging theory, Brønsted-Lowry definition is the definition most commonly used. In this definition, the acidity of a compound is determined by the stability of hydronium ion and conjugate base terlarutnya when the compounds were given protons to a solution of acid where it is located. Stability of the conjugate base showed higher acidity of the related compounds is higher.
System of acid / base different from redox reactions, there was no change in oxidation state in acid-base reaction.
System of acid / base different from redox reactions, there was no change in oxidation state in acid-base reaction.
The properties
In general, acids have the properties as follows:
• Flavor: sour when dissolved in water.
• Touch: acid stinging when touched, especially when the acid strong acid.
• reactivity: acid reacts violently with most metal, which is corrosive to metal.
• electrical conductivity: acid, although not always ionic, an electrolyte.
Chemical properties
In water, the following equilibrium reaction occurs between an acid (HA) and water, which acts as a
base,
HA + H2O ↔ A- + H3O+
Strong acids have large Ka values (ie, the reaction equilibrium is far to the right, there are a lot of H3O +; almost all acid decomposed). For example, the Ka value for hydrochloric acid (HCl) is 107.
Weak acids have small Ka values (ie, a number quite a lot of HA and A-are together in solution; a small amount of H3O + in solution; acid is only partially dissociated). For example, the value of Ka for acetic acid is 1.8 × 10-5.
Strong acid halide include acid - HCl, HBr, and HI. (However, hydrofluoric acid, HF, is relatively weak.) oxo acids, which generally contain a central atom had high oxidation states surrounded by oxygen, is also quite strong; include HNO3, H2SO4, and HClO4. Most organic acids are weak acids.
Weak acid solution and salt from the base konjugatnya forming a buffer solution.
The use of acid
Acid has a variety of uses. Acids are often used to remove rust from metal in a process called "pengawetasaman" (pickling). Acid can be used as an electrolyte in wet cell batteries, such as sulfuric acid used in car batteries. In humans and other animals, hydrochloric acid is part of the stomach acid is secreted in the stomach to help break down proteins and polysaccharides as well as change proenzim an inactive pepsinogen into the enzyme pepsin. Acid is also used as a catalyst, for example, sulfuric acid is widely used in the alkylation process of making gasoline.
Weak acids have small Ka values (ie, a number quite a lot of HA and A-are together in solution; a small amount of H3O + in solution; acid is only partially dissociated). For example, the value of Ka for acetic acid is 1.8 × 10-5.
Strong acid halide include acid - HCl, HBr, and HI. (However, hydrofluoric acid, HF, is relatively weak.) oxo acids, which generally contain a central atom had high oxidation states surrounded by oxygen, is also quite strong; include HNO3, H2SO4, and HClO4. Most organic acids are weak acids.
Weak acid solution and salt from the base konjugatnya forming a buffer solution.
The use of acid
Acid has a variety of uses. Acids are often used to remove rust from metal in a process called "pengawetasaman" (pickling). Acid can be used as an electrolyte in wet cell batteries, such as sulfuric acid used in car batteries. In humans and other animals, hydrochloric acid is part of the stomach acid is secreted in the stomach to help break down proteins and polysaccharides as well as change proenzim an inactive pepsinogen into the enzyme pepsin. Acid is also used as a catalyst, for example, sulfuric acid is widely used in the alkylation process of making gasoline.
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