Investigating the Effect of Concentration on the Temperature Rise, Heat Evolved and Heat of Neutralization for the Reaction Between HCl and NaOH

Investigating the Effect of Concentration on the Temperature Rise, Heat Evolved and Heat of Neutralization for the Reaction Between HCl and NaOH

Neutralization is the special name given for the reaction between an

acid and an alkali leading to the formation of water molecules and a

salt. The reactions between basic oxides, or hydroxides, and acids are

very important and are called neutralizations. Since the metallic ions

and anions from the acid do not change, the essential reaction of

neutralization is always the formation of non-ionized molecules of

water from the hydroxide and hydrogen ions.

H+ (aq) + OH-(aq) [IMAGE] H2o (l)

The following are examples of neutralizations. The metallic ions and

the negative ions from the acids remain to produce the salt.

½ H2+So4- (aq) + ½ Na+OH- (aq) → ½ Na+So4- (aq) + H2o (l)

Sulphuric acid Sodium hydroxide Sodium sulphate water

H+No3- (aq) + Na+OH- (aq) → Na+No3- (aq) + H2o (l)

Nitric acid Sodium hydroxide Sodium nitrate water

H+cl- (aq) + Na+OH- (aq) → Na+Cl- (aq) + H2o (l)

Hydrochloric acid Sodium hydroxide Sodium chloride water

Since all these reactions reduce to H+ + OH-→ H2o, the energy change

accompanying both should be the same. Because, in all the three

reactions only 1 mole of water is produced, and the metallic ions and

the negative ions in the acid are rather spectator ions and do not

participate in the reaction so much as to give an energy change. If

aqueous acidic solutions are made up containing one mole of ½ H2So4,

HNo3, and HCl in 25 cm3, and alkaline solutions containing one mole of

NaOH in 25 cm3 (strong acids and alkalis), any neutralization between

these solutions produces 1 mole of water and liberates the same amount

of heat energy and this heat is called Heat of neutralization which is

usually - 57.3 kJ. If a bond is broken, energy is needed and the

reaction is endothermic. However if a reaction is exothermic, it is a

recombination, which is bond making. Through this, energy is produced.