MCQ Detailed View

The heat of neutralization is the heat released when an acid reacts with a base to form water and salt. This reaction always gives out heat because it is an exothermic process. The amount of heat is measured in kilojoules per mole.

In the case of strong acids, they are fully broken into ions in water. For example, hydrochloric acid (HCl) gives hydrogen ions easily. When these hydrogen ions combine with hydroxide ions from a base, water is formed, and a large amount of heat is released. The value is almost the same for all strong acids, about –57 kJ per mole.

In the case of weak acids, they are not completely broken into ions. For example, acetic acid (CH₃COOH) remains partly in molecule form. Before neutralization, extra energy is needed to ionize the weak acid. Because of this, the total heat released is less compared to strong acids.

This shows a simple rule:

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  If the heat of neutralization is high, the acid is strong.

  
  


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  If the heat of neutralization is low, the acid is weak.

  
  

Strong acids like HCl, HNO₃, and H₂SO₄ always show greater heat values. Weak acids like CH₃COOH and H₂CO₃ show smaller values.

Therefore, the greater the heat of neutralization, the acid will be more strong. This concept helps in comparing different acids and understanding their behavior in chemical reactions.