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Neutralization is a chemical reaction in which an acid and a base react and produce salt and water. Neutralization is exothermic, meaning it produces heat.
Most generally, the following occurs:
Acid + Base ⇒ Salt + Water : ΔH = −C < 0
As an example — the reaction between hydrochloric acid and sodium hydroxide solutions:
HCl(aq) + NaOH(aq) ⇒ NaCl(aq) + H2O(l)
Since the HCl and NaOH dissociate into ions in solution, the ionic equation is:
H+ + Cl− + Na+ + OH− ⇒ Na+ + Cl− + H2O(l)
And since the sodium and chloride ions are just spectator ions not involved in the reaction, the net equation becomes:
H+ + OH− ⇒ H2O(l) : ΔHr = −56 kJ/mol
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 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 other neutralizing agent (antacids).
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