Acid Guide, Meaning , Facts, Information and Description
- For alternative meanings see acid (disambiguation).
An acid (represented by the generic formula AH) is typically a water-soluble, sour-tasting chemical compound. An acid always has a pH of less than 7. It is a molecule or ion that contains hydrogen or that is able to give up a proton to a base, or accept an unshared pair of electrons from a base. An acid reacts with a base in a neutralization reaction to form a salt.
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2 Characteristics 3 Acids in Food 4 Different Definitions of Acid/Base 5 Acid number 6 Neutralization 7 Some Common Acids |
Chemical Characteristics
In water, there is the following reaction:
There is a distinction between weak acids and strong acids. For a strong acid, no AH remains in solution:
That is why the acidity constant is only defined for weak acids:
Acidic (chemistry), the opposite to basic, reacting with basics to form salts. Acidic (geology), of rock: containing more than 65% of silica.
Characteristics
Acids are generally:
Acids in Food
Different Definitions of Acid/Base
The word acid comes from the Latin acidus meaning sour. Chemically though the term acid has a more specific meaning.
The Swedish chemist Svante Arrhenius defined an acid to be a substance that gave up hydrogen ions (H+) when dissolved in water, while bases are substances that give up hydroxide ions (OH-). Notice that this definition limits acids and bases to substances that can dissolve in water. Later on, Bronsted and Lowry defined an acid to be a proton donor and a base to be a proton acceptor. In this definition, even substances that are insoluble in water can be acids and bases. The most general definition of acids and bases is the Lewis definition. A Lewis acid is an electron acceptor, while a Lewis base is an electron donor. Acid/base systems are different from redox reactions in that there is no change in oxidation state.
The Lewis definition can be explained with molecular orbital theory. In general an acid can receive an electron pair in it's lowest unoccupied orbital LUMO from the highest occupied orbital HOMO of a base. That is, HOMO from the base and LUMO from the acid is combined to a bonding molecular orbital. Simpler definitions are often sufficient for many situations. An acid is often said to be a proton donor, that is the Brønsted definition above. In this case, the proton (H+) is the actual acid and the acidity of the proton-donating-compound, called an organic acid, is determined by its stability when it donates protons to the solution it is embedded in. So if the organic acid likes letting protons go, it has high acidity because it donates protons with empty molecular orbitals to the solution. This is how organic acids work, here the Brønsted definition is nice for calculations while the Lewis definition is good for understanding.
Acid number
This is used to quantify oxidation. It is the quantity of base, expressed in milligrams of potassium hydroxide, that is required to neutralize the acidic constituents in 1 g of sample.
AN = (Veq-beq)×N×56.1/Woil ).
Veq is the amount of titrant (ml) consumed by crude oil sample and 1ml spiking solution at the equivalent point, and beqbeq is the amount of titrant (ml) consumed by 1ml spiking solution at the equivalent point.
The molarity concentration of titrant (N) is calculated as such: N = 1000×WKHP/(204.23×Veq).
In which, WKHP is the amount (g) of KHP in 50ml of KHP standard solution, and Veq is the amount of titrant (ml) consumed by 50ml KHP standard solution at the equivalent point.
Acid number (mgKOH/g oil) for biodiesel is preferred to be lower than 3.
Neutralization
Neutralization is a type of reaction between an acid and a base. The products include salt and water. So, it is also called a water forming reaction
Example:
Strong Inorganic Acids
This is an Article on Acid. Page Contains Information, Facts Details or Explanation Guide About Acid Some Common Acids
Weak Inorganic Acids
Weak Organic Acids