Question

What is meant by acid-base neutralization? Write a net ionic equation to go along with your answer.

Short answer

Acid-base neutralization is a chemical reaction between an acid and a base, resulting in the formation of water and a salt. It can be understood as a reaction in which a proton (H+) from an acid combines with a hydroxide ion (OH-) from a base to form water (H2O). The remaining cation and anion from the initial reactants form a salt. For example, the net ionic equation for the neutralization between hydrochloric acid (HCl) and sodium hydroxide (NaOH) is: \( H^{+}(aq) + OH^{-}(aq) \rightarrow H_{2}O(l) \)

Step-by-step solution

Define Acid-Base Neutralization

Acid-base neutralization is a chemical reaction that occurs between an acid and a base, resulting in the formation of water and a salt. This process can be understood as a reaction in which a proton (H+) from an acid combines with a hydroxide ion (OH-) from a base to form water (H2O). The remaining cation and anion from the initial reactants form a salt.

Choose an Acid and a Base for the Example

Let's consider a simple example of an acid-base neutralization reaction. We'll use hydrochloric acid (HCl - a strong acid) and sodium hydroxide (NaOH - a strong base) for this demonstration.

Write the Balanced Chemical Equation

Write the balanced chemical equation for the reaction between hydrochloric acid and sodium hydroxide: HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l) This balanced equation shows that one molecule of hydrochloric acid reacts with one molecule of sodium hydroxide to produce one molecule of sodium chloride (the salt) and one molecule of water.

Write the Total Ionic Equation

The total ionic equation shows all of the ions present in the reaction. To write the total ionic equation, break the reactants and products into their respective ions: H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq) → Na+(aq) + Cl-(aq) + H2O(l)

Write the Net Ionic Equation

The net ionic equation is derived from the total ionic equation by cancelling out the spectator ions, which are the ions that do not participate in the reaction (Na+ and Cl-, in this case). The net ionic equation for the acid-base neutralization between hydrochloric acid and sodium hydroxide is: H+(aq) + OH-(aq) → H2O(l) This equation illustrates the key process in an acid-base neutralization: the combination of a proton (H+) from an acid and a hydroxide ion (OH-) from a base to form water.

Key concepts

Net Ionic Equation

In chemistry, a net ionic equation is essential for understanding the underlying principles of a reaction, especially in solutions. It focuses on the ions and molecules directly involved in the reaction. To form a net ionic equation, we first write the total ionic equation by breaking all strong electrolytes into their ions. For example, in the reaction between hydrochloric acid (HCl) and sodium hydroxide (NaOH), we begin with the total ionic representation:

• H⁺(aq) + Cl^-(aq) + Na⁺(aq) + OH^-(aq) → Na⁺(aq) + Cl^-(aq) + H₂O(l)

The net ionic equation is achieved by removing the spectator ions, which are ions present on both sides of the equation and do not participate in the chemical change. This leaves us with:

• H⁺(aq) + OH^-(aq) → H₂O(l)

This equation shows the actual chemical change: the formation of water, which is central to acid-base neutralization.

Proton Transfer

Proton transfer is a fundamental concept in acid-base reactions. It refers to the movement of a proton (H⁺ ion) from the acid to the base. In the classic example of hydrochloric acid (HCl) reacting with sodium hydroxide (NaOH), hydrochloric acid provides the proton.

The hydroxide ion (OH^-), present in the sodium hydroxide, accepts this proton. This is the essence of acid-base neutralization, where:

• The acid gives away (donates) a proton.
• The base receives (accepts) the proton.

This transfer results in the creation of a water molecule (H₂O). Understanding proton transfer helps clarify why certain substances act as acids while others function as bases. It is the key step that drives the neutralization process, transforming the reactive ions into water.

Spectator Ions

In chemical reactions, especially in solutions, not all ions participate actively. These non-participating ions are known as spectator ions. They exist in the same form on both sides of a chemical equation and do not affect the outcome of the reaction. In our reaction example:

• HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)

The sodium (Na⁺) and chloride (Cl^-) ions are spectator ions. They don’t partake in the chemical process of neutralization. Instead, they simply "watch" the core reaction, which is between the hydrogen ion (H⁺) and the hydroxide ion (OH^-).

Identifying spectator ions is important because they can be removed to simplify reactions. This simplification yields the net ionic equation, highlighting only the active components of a reaction.

Water Formation

Water formation is the definitive outcome of an acid-base neutralization reaction. Whenever an acid reacts with a base, the probability is high that the result will include water. In the reaction between hydrochloric acid and sodium hydroxide:

• H⁺(aq) + OH^-(aq) → H₂O(l)

This equation exemplifies the process perfectly. A proton from the acid (H⁺) reacts with the hydroxide ion (OH^-) from the base, resulting in water formation.

This process is a classic example of neutralization. The resulting water produced is generally neutral with a pH of 7. It’s fascinating to consider that these simple ions can combine to form such a fundamental substance, showcasing the elegance of chemical reactions.

Chemical Reaction

A chemical reaction involves the breaking and making of bonds, leading to a transformation of substances. In an acid-base neutralization, it occurs when acids react with bases to form water and salt. The classic example of a chemical reaction is:

• HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)

Here, hydrochloric acid (an acid) reacts with sodium hydroxide (a base) to yield sodium chloride (a salt) and water.

Key aspects of chemical reactions include:

• Molecular rearrangement.
• Energy change, often perceived as heat.
• Creation of new products (like water and salt here).

Understanding a chemical reaction involves recognizing these interactions and changes, providing insight into how substances interact in the world of chemistry. The formation of water and salt exemplifies how reactants transform during neutralization, a common and significant type of chemical reaction.