Heat of nuetralization

Neutralization reaction is a type of reaction where by an acid reaction with a base to produce salt and water only.

Heat of neutralization is the amount of heat evolved when one mole of acid reacts with one mole of an alkaline to form one mole of water. All heat of neutralization is exothermic reactions. It can also be defined as the heat released when one mole of water is formed.

The standard heat of neutralization is the amount of heat liberated when one mole of hydrogen ion and hydroxide ion reacts to form one mole of water under standard conditions of 298k and one atmosphere.

The heat liberated is given by the formula: Q= mcpT

Where

M is the mass of solution

Cp is the specific heat capacity of the solution

T is the temperature change

And the enthalpy change (H)= Q/n

n is the number of moles of the substance.

In an experiment of weak solutions; such as dilute sulfuric acid and sodium hydroxide, the compounds ionize. The only change that occurs is the formation of water molecules. Therefore the heat of neutralization is the heat of solution. In the above example, the enthalpy involved is -57.4kj/mol

H+ + OH                           H2O

Also the heat of neutralization between two strong acid and base is approximately the same. Example;

KOH + HCl              KCl  +H2O             H=54.3 kj/mol.

This is possible because of the dissociation between the compounds involved into different ions.

When a weak base and acid reacts, the heat of neutralization deceases; this accounts that the compounds dissociate partially in their solution. So the energy loss is the energy used in breaking the un-dissociated molecules apart in order to bring complete dissociation.



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