The correct dissociation equation illustrates how a compound breaks apart into its constituent ions when dissolved in a solution, typically water. The specific form of the equation depends on whether the substance is an acid or a base.
Understanding Dissociation
Dissociation is the process where ionic compounds, acids, or bases separate into smaller ions when dissolved in a solvent. This process is fundamental to understanding the properties of solutions, such as their conductivity and pH. The arrow in these equations signifies the separation of the compound into ions.
Dissociation Equations for Acids
Acids are substances that, when dissolved in water, donate hydrogen ions (H⁺) to the solution. The general form for the dissociation of a strong acid, which fully dissociates in water, is:
- General Form: HA → H⁺ + A⁻
Here, 'HA' represents the acid molecule, 'H⁺' is the hydrogen ion (often represented as H₃O⁺ in water to show its association with water molecules, but H⁺ is commonly used in simplified dissociation equations), and 'A⁻' is the conjugate base or the remaining anion.
Example:
The dissociation of hydrochloric acid (HCl), a strong acid, in water is represented as:
- Hydrochloric Acid: HCl → H⁺ + Cl⁻
This equation shows that when HCl dissolves, it completely breaks apart into a hydrogen ion and a chloride ion.
Dissociation Equations for Bases
Bases are substances that, when dissolved in water, release hydroxide ions (OH⁻) into the solution. For strong bases, which completely dissociate, the general form of the dissociation equation is:
- General Form: BOH → B⁺ + OH⁻
In this form, 'BOH' represents the base molecule, 'B⁺' is the cation formed from the base, and 'OH⁻' is the hydroxide ion.
Example:
The dissociation of sodium hydroxide (NaOH), a common strong base, in water is:
- Sodium Hydroxide: NaOH → Na⁺ + OH⁻
This equation indicates that NaOH dissociates completely into a sodium ion and a hydroxide ion when dissolved.
Key Components of Dissociation Equations
Each part of a dissociation equation conveys important information:
- Reactant (left side): The original compound (e.g., HA, BOH) that is dissolving.
- Arrow (→): Indicates the process of dissociation, showing that the compound is breaking apart into ions. For strong acids and bases, a single arrow is used to denote complete dissociation.
- Products (right side): The ions that are formed when the compound dissociates (e.g., H⁺, A⁻, B⁺, OH⁻).
Summary Table of Dissociation Equations
The following table summarizes the general forms and examples for both acid and base dissociation:
| Type of Substance | General Dissociation Equation | Example |
|---|---|---|
| Acid | HA → H⁺ + A⁻ | HCl → H⁺ + Cl⁻ |
| Base | BOH → B⁺ + OH⁻ | NaOH → Na⁺ + OH⁻ |
These equations are fundamental to understanding chemical reactions in aqueous solutions, especially in the context of acid-base chemistry.
