Neutralization

Neutralization

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In chemistry, neutralization, or neutralisation (see spelling differences) is a chemical reaction
Chemical reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...

 in which an acid
Acid
An acid 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...

 and a base
Base (chemistry)
For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...

 react to form a salt. Water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 is frequently, but not necessarily, produced as well. Neutralizations with Arrhenius acids and bases always produce water:
YOH + HX → XY + H2O

Y and X represent a monovalent cation and anion respectively. XY would be the salt produced. An example reaction of this form is the reaction between sodium hydroxide and hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....

, where sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 is Y and chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...

 is X:
HCl + NaOH → NaCl + H2O

Water and common table salt are produced.

The reaction can also be considered as a net ionic equation:
H+ + OH- → H2O

This representation is inaccurate, however, as the hydrogen ion (H+) does not actually occur in solution during a neutralization. In fact, the hydronium ion (H3O+) occurs, produced by the following reaction:
H+ + H2O → H3O+

Considering the hydronium ion, the actual net ionic reaction occurring is:
H3O+ + OH- → 2H2O


In non-aqueous reactions, water is less likely to be formed; however, there is always a donation of protons (see Brønsted-Lowry acid-base theory). Since a variety of definitions of acids and bases exist, a variety of reactions may be considered neutralization reactions. All of the following may be considered neutralization reactions under different definitions:
HCl + NaOH → NaCl + H2O
2HCl + Mg → MgCl2 + H2

2HCO2H + MgO → Mg(HCO2)2 + H2O

HF + NH3 → NH4F


Often, neutralization reactions are exothermic
Exothermic
In thermodynamics, the term exothermic describes a process or reaction that releases energy from the system, usually in the form of heat, but also in the form of light , electricity , or sound...

 (the enthalpy of neutralization). For example, the reaction of sodium hydroxide and hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....

. An example of an endothermic
Endothermic
In thermodynamics, the word endothermic describes a process or reaction in which the system absorbs energy from the surroundings in the form of heat. Its etymology stems from the prefix endo- and the Greek word thermasi,...

neutralization is the reaction between sodium bicarbonate (baking soda)
Sodium bicarbonate
Sodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula Na HCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda . The natural mineral form is...

 and acetic acid (vinegar)
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...

.

Neutralization means to neutralize, in chemistry the neutral PH of 7 would be counted as neutral.

Applications

  • Chemical titration
    Titration
    Titration, also known as titrimetry, is a common laboratory method of quantitative chemical analysis that is used to determine the unknown concentration of an identified analyte. Because volume measurements play a key role in titration, it is also known as volumetric analysis. A reagent, called the...

     methods are used for analyzing acids or bases to determine the unknown concentration
    Concentration
    In chemistry, concentration is defined as the abundance of a constituent divided by the total volume of a mixture. Four types can be distinguished: mass concentration, molar concentration, number concentration, and volume concentration...

    . Either a pH meter
    PH meter
    A pH meter is an electronic instrument used for measuring the pH of a liquid...

     or a pH indicator
    PH indicator
    A pH indicator is a halochromic chemical compound that is added in small amounts to a solution so that the pH of the solution can be determined visually. Hence a pH indicator is a chemical detector for hydronium ions or hydrogen ions in the Arrhenius model. Normally, the indicator causes the...

     which shows the point of neutralization by a distinct color change can be employed. Simple stoichiometric calculations with the known volume of the unknown and the known volume and molarity of the added chemical gives the molarity of the unknown.
  • Excess gastric acid
    Gastric acid
    Gastric acid is a digestive fluid, formed in the stomach. It has a pH of 1 to 2 and is composed of hydrochloric acid , and large quantities of potassium chloride and sodium chloride...

     in the stomach (acid indigestion) is typically neutralized by the ingestion of sodium bicarbonate
    Sodium bicarbonate
    Sodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula Na HCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda . The natural mineral form is...

     (NaHCO3) or another neutralizing agent such as an antacid.
  • Neutralization can also be used to reduce the pain of insect and plant stings. Bee stings can be neutralized with alkalines and wasps with acids. (This does not actually reduce the pain, the acidity of the sting is not what causes itching but other chemicals in the venom. The reason the pain is reduced is merely psychological).
  • In wastewater treatment
    Water treatment
    Water treatment describes those processes used to make water more acceptable for a desired end-use. These can include use as drinking water, industrial processes, medical and many other uses. The goal of all water treatment process is to remove existing contaminants in the water, or reduce the...

    , chemical neutralization methods are often applied to reduce the damage that an effluent may cause upon release to the environment. For pH control, popular chemicals include calcium carbonate
    Calcium carbonate
    Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...

    , calcium oxide
    Calcium oxide
    Calcium oxide , commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline crystalline solid at room temperature....

    , magnesium hydroxide
    Magnesium hydroxide
    Magnesium hydroxide is an inorganic compound with the chemical formula Mg2. As a suspension in water, it is often called milk of magnesia because of its milk-like appearance. The solid mineral form of magnesium hydroxide is known as brucite....

    , and sodium bicarbonate
    Sodium bicarbonate
    Sodium bicarbonate or sodium hydrogen carbonate is the chemical compound with the formula Na HCO3. Sodium bicarbonate is a white solid that is crystalline but often appears as a fine powder. It has a slightly salty, alkaline taste resembling that of washing soda . The natural mineral form is...

    . The selection of an appropriate neutralization chemical depends on the particular application.

Neutralization is American and Neutralisation is Australian/UK
In chemistry if anything has a pH of 7 it is considered to be a neutral.

Calculations


Equal numbers of moles
Mole (unit)
The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...

of acid and base are needed for neutralization reactions. Hence, the formula becomes
a × [A] × Va = b × [B] × Vb


where a is the number of acidic hydrogens and b is the constant that tells you how many H3O+ ions the base can accept. [A] denotes the concentration of acid and [B], the concentration of base. Va is the volume of acid and Vb is the volume of base.