Dissociation is also called dissociation. In chemistry, it refers to the process of compound splitting to form ions or atomic clusters. There are two meanings, one is that diatomic gas is heated and separated into its constituent atoms, the other is that compounds are separated into positive and negative charged ions in water. Both chemical reactions are labeled dissociation. For the second case, dissociation and ionization are synonymous. It can be carried out in gas, liquid, solid or solution state.
In addition, "dissociation" refers to the combination of "dissociation" and "interpretation" in Zhouyi.
dissociation
molecule separate or thermal decomposition In two or more parts（ atom 、 molecule 、 Ions 、 Group ）Process. [1] For example, when some ionic compounds are heated and melted, the original lattice is destroyed to form free moving anions and cations, such as sodium chloride and potassium nitrate; When ionic compounds are dissolved in water, anions and cations are hydrated respectively, reducing the original attraction between anions and cations, forming hydrated anions and cations, and dissociation occurs, such as copper sulfate aqueous solution; Some covalent compounds dissociate into hydrated anions and cations in water, such as hydrogen chloride dissolved in water to form H + (aq) and Cl - (aq) and so on are dissociation. Dissociation There are two cases:
① electrolyte Of Ionization 。 The first is that the electrolyte is soluble in water ionization by anion and cation , such as sodium chloride Soluble in water, forming Na + And Cl - 。 For example, acetic acid (CH three COOH) dissolves in water, and the ionic bond breaks to form acetate ion (CH three COO - ）。 The hydrogen atom in it becomes a hydrogen ion (actually a proton) and combines with water to form H three O + 。 This reaction can be described by the ionic equation as follows:
CH three COOH + H two O → H three O + + CH three COO -
But generally speaking, for the sake of simplicity, the reaction between hydrogen ion and water can not be written, so the above reaction can be simply described as:
CH three COOH → H + + CH three COO -
Due to its special properties (can be electrolyzed into H and OH), water can make the solution acidic or alkaline after ionic reaction. Such as ammonia (NH three ·H two O）， In fact, it can be understood that water gives ammonia a proton, namely:
NH three + H two O → NH four + + OH -
The second is some Ionic compound be heated melt Later, the original lattice It is destroyed to form anion and cation that can move freely Molten body can electric conduction 。 Some ionic compounds (such as NaCl) are melted by heat, and the original lattice is destroyed, dissociating into anions (Cl - ）And cation (Na + )； ② Certain Decomposition 。 For example, diatomic gas molecules (such as Cl two ）It dissociates its constituent atoms (Cl) after heating. Reversible decomposition reaction It is also a dissociation reaction, such as Phosphorus pentachloride Exploded into Phosphorus trichloride and chlorine Reaction of: PCl five ⇋ PCl three +Cl two 
leave
solution
