Neutralization
From Wikipedia, the free encyclopedia
- This article is about neutralization in chemistry. For the use of this term in linguistics, see Phoneme#Neutralization, archiphoneme, underspecification.
Neutralization is a chemical reaction, also called a water forming reaction, in which an acid and a base or alkali (soluble base) react and produce a salt and water. In other words, it can be said that neutralization is the combination of hydrogen ions H+ and hydroxide ions OH− (or oxide ions O2−) to form water molecule H2O. In the process, a salt is formed. Neutralization is exothermic, meaning it produces heat.
Most generally, the following occurs:
- acid + base → salt + water
For example, the reaction between hydrochloric acid and sodium hydroxide solutions:
- hydrochloric acid + sodium hydroxide → sodium chloride + water
- HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
Since the HCl and NaOH dissociate into ions in solution, the ionic equation is:
- H+(aq) + Cl−(aq) + Na+(aq) + OH−(aq) → Na+(aq) + Cl−(aq) + H2O(l)
And since the sodium and chloride ions are just spectator ions not involved in the reaction, the net equation becomes:
- H+(aq) + OH−(aq) → H2O(l) : ΔrH = −55.90 kJ mol−1
This illustrates why neutralization reactions are also referred to as water forming reactions. Of course the sodium and chloride ions are still in solution so the result is pH neutral salt water.
Chemical titration methods are used for analyzing acids or bases to determine the unknown concentration. A pH meter can be used to determine the point of neutralization or a pH indicator such as UI (universal indicator) which shows the point of neutralization by a distinct color change can be used. 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 in the stomach (acid indigestion) is typically neutralized by the ingestion of sodium bicarbonate (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 alkalis and wasps with acids. Nettle stings can be neutralised with alkalis like the one found in dock leaves.
Equal amounts (numbers of moles) of acid and base are needed for neutralization reactions between strong acids and strong bases. Use the formula:
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.
