The reaction between an acid and a base is called a neutralization reaction.
Neutralization
NaOH + HCl
==>
NaCl + HOH
NaOH (aq) + HCl (aq)
==>
NaCl (aq) + HOH (liq)
General Reaction
The active species of a reaction are easily identified when ionic reactants form a molecular species or when there is a change in oxidation states.
Molecular Reaction
Full ionic reaction
Na + (aq) + OH (aq) + H + (aq) + Cl - (aq)
==>
Na + (aq) + Cl - (aq) + HOH (liq)
Net Ionic Reaction
OH - (aq) + H + (aq)
==>
HOH (l)
In net ionic reactions all spectator ions are removed and only those atoms, molecules or ions that are actually involved in the reaction are included. For neutralization reactions the net ionic reaction has no spectator ions, Na + (aq) and Cl - (aq). The spectator ions can be replaced with other ions provided by the needed acid and base.
Thermochemistry is a study of the quantity of heat absorbed or evolved by chemical reactions.
In calorimetry, the heat evolved or absorbed by a chemical reaction is inferred by measuring temperature changes in an insulated reaction vessel.
The neutralization of a strong acid and strong base, represented by the equation below is highly exothermic.
HCl (aq) + NaOH (aq) ==> NaCl (aq) + H
2
O H rxn
= ?
The heat (enthalpy) of neutralization is the heat evolved in an acid-base reaction.
Related terms: enthalpy of reaction, enthalpy of neutralization, (molar) heat of reaction.
To measure the heat of neutralization, (molar heat of reaction), between hydrochloric acid and sodium hydroxide, mix equal moles of HCl solution and NaOH in the calorimeter and measure the temperature change of the solution inside the calorimeter.
The law of conservation of energy is the basis for calculating the reaction heat (assume no heat lost to the surrounding).
Q rxn
+ Q soln
= 0 therefore Q rxn
= - Q soln
Q rxn is the heat generated by the reaction (negative value)
Q rxn is the measured experimental heat of reaction for the amount of HCl/NaOH used.
Q soln
is the heat absorbed by the solution and is reflected by the temperature change.
Q soln
= m soln
* C soln
* T where is m soln is the mass, C soln
is the specific heat capacity, and
T is the temperature change of the solution.

You can separate the two enthalpy changes that occur inside the calorimeter.
∆ H system
= ∆ H
Therefore, ∆ H reaction
+ ∆ H reaction temp.
= – ∆ H
= 0 . temp.
∆ H reaction
= – C system
∆ T.
The molar heat of reaction is found by dividing the Q rxn by the mole value of the smaller of the NaOH moles or HCl moles used in the reaction.
Use the molar quantities of reactants to calculate the molar enthalpy of neutralization,
∆ H neutralization, in kJ/mol. The heats of neutralization of all strong acid-base pairs are identical. For strong acids and bases the accepted value for ∆ H neutralization is -57.7 kJ/mol (56.4J/C)
You may remember the density of water is 1.00g/mL, not 1.04g/mL and its heat capacity is 4.18J/gC. But our reaction is a neutralization reaction and produces saltwater, whose density is 1.04g/mL and heat cap. is 3.89J/gC. Also, we are determining the molar heat of neutralization. Our solutions are 2 M for 50mL, so you must adjust this to 1 mole for 1
L.
When any strong acid is mixed with any strong base, the heat of neutralization is always about 13,700 calories for each equivalent weight of acid and base neutralized.
13.3 kcal/mole
B. Heat of neutralization
The amount of energy evolved when 1 mole of H (from an acid) combines with 1 mole of OH (from a base) to form 1 mole of water.
NaOH + HCl = NaCl + H
2
O q = -56.2 kJ