1. Basic concept of acid-base neutralization reaction:
Acid-base neutralization reaction refers to a chemical reaction in which acid and alkali react under appropriate conditions to produce salt and water. In the process of neutralization, hydrogen ions (H+) and hydroxyl ions (OH-) combine between acid and alkali, and finally water molecules are generated.
2. Exothermic reaction:
2. 1 definition: exothermic reaction refers to the reaction that releases heat during the reaction. In the acid-base neutralization reaction, if the heat capacity of the generated water molecules is less than that of the acid-base solution before the reaction, the reaction is exothermic.
2.2 Reason: The exothermic reaction occurs because the formation of chemical bonds releases more energy during the reaction, which leads to the decrease of internal energy in the reaction system, thus releasing heat.
3. Endothermic reaction:
3. 1 Definition: Endothermic reaction refers to the reaction that absorbs heat during the reaction. In the acid-base neutralization reaction, if the heat capacity of the generated water molecules is greater than that of the acid-base solution before the reaction, the reaction is endothermic.
3.2 Reason: Endothermic reaction occurs because in the reaction, the fracture of chemical bonds needs to absorb external heat to overcome the activation energy of the reaction and increase the internal energy of the reaction system.
Expand knowledge:
Heat capacity: heat capacity refers to the proportional relationship between the heat absorbed or released by an object when the temperature changes and the temperature changes. Heat capacity can be used to describe the ability of a substance to react to heat.
In the acid-base neutralization reaction, the change of solution heat capacity before and after the reaction is related to the reaction type, which determines whether the reaction is exothermic or endothermic.
Neutralization heat: Neutralization heat refers to the heat released or absorbed by unit mole of acid-base reaction. According to the positive and negative values of reaction heat, it can be judged whether the acid-base neutralization reaction is exothermic or endothermic. For example, when the neutralization reaction is exothermic, the neutralization heat is negative; When the neutralization reaction absorbs heat, the neutralization heat is positive.
Factors affecting the exothermic or endothermic reaction of acid-base neutralization: the nature and concentration of chemical substances in the reaction system; Reaction temperature; The speed of the reaction.
Practical application: The exothermic or endothermic nature of acid-base neutralization reaction has many practical applications in life. For example, the exothermic characteristics of acid-base neutralization reaction can be used in the design and application of heat preservation, heating and temperature regulation equipment; The endothermic characteristics of acid-base neutralization reaction can be used in endothermic agent, refrigeration, ice making and other fields.
Summary: The exothermic or endothermic reaction of acid-base neutralization depends on the properties of acid-base solution, reaction conditions and the characteristics of reaction systems involved in the reaction. Exothermic reaction will release heat, endothermic reaction will absorb heat. Therefore, in the specific acid-base neutralization reaction, it is necessary to judge whether the reaction is exothermic or endothermic according to the experimental conditions and the properties of reactants.