Question

Use the Arrhenius definition of acids and bases to write the net ionic equation for the reaction of an acid with a base.

Short answer

According to the Arrhenius definition of acids and bases, an acid produces hydrogen ions (H+) when dissolved in water, and a base produces hydroxide ions (OH-) when dissolved in water. The general reaction between an acid and a base is represented as HA(aq) + BOH(aq) -> BA(aq) + H2O(l). After dissociating the reactants and eliminating the spectator ions, the net ionic equation for the reaction of an acid with a base is: \[H^{+}(aq) + OH^{-}(aq) \rightarrow H_{2}O(l)\].

Step-by-step solution

General equation

Acid + Base -> Salt + Water Now, let's represent the acid as HA and the base as BOH. Here, H represents the hydrogen ion and A represents the anion of the acid, while B represents the cation and OH represents the hydroxide ion of the base.

Reaction representation

HA(aq) + BOH(aq) -> BA(aq) + H2O(l) Next, we will dissociate the reactants into their respective ions.

Dissociation of reactants

H+(aq) + A-(aq) + B+(aq) + OH-(aq) -> BA(aq) + H2O(l) As the salt (BA) is formed, its ions are still dissociated in the solution. So, we will also dissociate BA into its ions.

Dissociation of salt

H+(aq) + A-(aq) + B+(aq) + OH-(aq) -> B+(aq) + A-(aq) + H2O(l) Now, we can see that B+ and A- ions are present on both the reactants and products side, so they act as spectator ions and can be removed from the equation.

Elimination of spectator ions

H+(aq) + A-(aq) + B+(aq) + OH-(aq) -> B+(aq) + A-(aq) + H2O(l) Finally, we get the net ionic equation for the reaction of an acid with a base according to the Arrhenius definition.

Net ionic equation

H+(aq) + OH-(aq) -> H2O(l)

Key concepts

Net Ionic Equation

Understanding the net ionic equation is crucial for grasping the fundamentals of acid-base chemistry. Let's simplify the concept: A net ionic equation is a chemical equation that shows only the ions and molecules directly involved in the chemical reaction. In the provided step by step solution, we eliminated the spectator ions to focus on the key players in the acid-base reaction.

In essence, the net ionic equation for an acid reacting with a base to form water highlights the active participants. In our example, hydrogen ions (H^+(aq)) from the acid and hydroxide ions (OH^-(aq)) from the base combine to produce water (H2O(l)), which is shown in the final equation:H^+(aq) + OH^-(aq) -> H2O(l).

This process is akin to filtering out the noise to highlight the essence of the conversation. By understanding and writing net ionic equations, students can better visualize and comprehend the key transformations during a chemical reaction.

Acid-Base Reaction

An acid-base reaction, according to the Arrhenius definition, occurs when an acid and a base interact to form water and a salt. Acids are substances that release hydrogen ions (H^+) when dissolved in water, whereas bases are substances that release hydroxide ions (OH^-).

The reaction between an acid and a base is a prime example of a neutralization reaction, where the properties of the acid and base cancel each other out, leading to the formation of water (H2O) and a salt. In our textbook exercise, the acid (HA) donates a hydrogen ion to the base (BOH), and the remaining ions combine to form a salt (BA). The reaction can be visualized in simple terms:
HA (acid) + BOH (base) -> BA (salt) + H2O (water).

This reaction has various practical applications, from the neutralization of acidic soil to the making of common household products like soap.

Dissociation of Reactants

Dissociation is a process where ionic compounds separate into their ions when dissolved in water. In our exercise, we witnessed the dissociation of reactants where the acid (HA) and the base (BOH) divided into their constituent ions in aqueous solution.

For example, when an acid like hydrochloric acid (HCl) dissolves in water, it dissociates like so:
HCl (aq) -> H^+(aq) + Cl^-(aq).
Similarly, when a base, such as sodium hydroxide (NaOH), dissolves, it dissociates into:Na^+(aq) + OH^-(aq).

This understanding of dissociation is vital as it sets the stage for predicting the outcomes of reactions. Without dissociation, there would be no free ions to participate in the chemical change that defines an acid-base reaction.

Spectator Ions

In any aqueous reaction, some ions do not participate in the actual chemical change; these are called spectator ions. They appear unchanged on both the reactant and the product side of a chemical equation. In our acid-base example, we identified B^+(aq) and A^-(aq) as the spectator ions because they did not contribute to the formation of water, the key event of this reaction.

Why are spectator ions important? They help simplify the equation to its essence, leading to the net ionic equation. By removing spectator ions, we can highlight the actual chemical transformation. This simplification allows students to focus on the reaction's essence without the distraction of these chemically inactive players. Spectator ions can be thought of as part of the audience in a play — present but not acting on the stage.