The chemical process of neutralisation is essentially a reaction between an acid and a base to produce a solution that is neither acidic or basic. The chemistry behind neutralisation reactions is not overly complex and the reaction itself only yields two products. You can understand why the products form by considering the concepts of acids and a bases.
Acids, Bases and pH
Chemistry has several definitions of an acid and base, but one of the most easily understood is the Bronsted-Lowry definition, which says that an acid can donate a positive hydrogen ion (H+), while a base can accept H+. Strong acids, such as HCl, are therefore chemicals that release a large amount of H+ when dissolved in water. Strong bases generally release hydroxide ion (OH-), which can combine with H+. The pH of a solution is a measure of acidity and is related to the H+ concentration; a high level of H+ means an acidic solution and a low pH value.
Pure water has only a very small amount of free H+ and a pH of 7, which is considered neutral. When a strong acid such as HCl is added, the acid greatly increases the H+ concentration of the solution and the resulting mixture is acidic. If an equivalent amount of a strong base such as NaOH is then mixed into this acidic solution, the base will counteract that of the acid and the pH will return to neutral. Similarly, adding a strong acid to a basic solution will neutralise it.
Chemical Products of Neutralization
When a strong acid and base combine in a neutralisation reaction, the H+ of the acid combines with the OH- of the base and forms H2O, or water. This is an essential component of the neutralisation, since it ties up both the H+ and OH- to produce neutral water. The remaining portions of the acid and base molecules also combine to form a compound known generically as a salt. In the case of HCl and NaOH, the sodium ion (Na+) and chloride ion (Cl-) combine to form common table salt, NaCl. Since the reaction produces water, and salts are highly soluble, what is formed is actually a solution of dissolved salt.
The other product that typically results from a neutralisation reaction is heat. Most reactions between strong acids and bases are "exothermic," which means that they produce heat as they occur. This means that a mixture of a strong acid and a strong base will heat up as they react. Therefore, the final product of a neutralisation reaction will be a warm solution of a salt in water. In terms of a chemical reaction, you can write out the example of hydrochloric acid and sodium hydroxide as HCl + NaOH --> H2O + NaCl + heat.