Problem 90 - Introductory Chemistry Atoms First

Question

Consider the neutralization reaction that occurs upon the reaction of aqueous potassium hydroxide with aqueous hydrochloric acid. (a) Write a complete ionic equation for this neutralization reaction. (b) Write a net ionic equation for this neutralization reaction.

Step-by-Step Solution

Answer

The complete ionic equation for the neutralization reaction between aqueous potassium hydroxide and aqueous hydrochloric acid is: \(K^+(aq) + OH^-(aq) + H^+(aq) + Cl^-(aq) \rightarrow K^+(aq) + Cl^-(aq) + H_2O(l)\). The net ionic equation for this reaction is: \(H^+(aq) + OH^-(aq) \rightarrow H_2O(l)\).

Step 1: 1. Balanced Chemical Equation

To begin, we need to write the balanced chemical equation for the neutralization reaction between aqueous potassium hydroxide (KOH) and aqueous hydrochloric acid (HCl). In a neutralization reaction, an acid (HCl) reacts with a base (KOH) to produce water (H_2O) and a salt (KCl). The balanced equation for the reaction is: KOH(aq) + HCl(aq) → KCl(aq) + H_2O(l)

Step 2: 2. Complete Ionic Equation

Next, we need to write the complete ionic equation. To do that, we'll break apart the aqueous species, KOH(aq) and HCl(aq), into their respective ions according to their solubility in water. The complete ionic equation is: K^+(aq) + OH^-(aq) + H^+(aq) + Cl^-(aq) → K^+(aq) + Cl^-(aq) + H_2O(l)

Step 3: 3. Net Ionic Equation

Now, lastly, we need to write the net ionic equation. To write the net ionic equation, remove any spectator ions that don't participate in the reaction. In this case, potassium ion (K+) and chloride ion (Cl-) are spectator ions, as they remain the same on both sides of the equation. The net ionic equation is: H^+(aq) + OH^-(aq) → H_2O(l)

Key Concepts

Ionic Equations

In chemistry, an ionic equation helps us to understand how different ions participate in a chemical reaction. These equations show the ions that are involved in the reaction after substances are dissolved in water. When compounds dissolve, they split into their respective ions. For example:

• Potassium hydroxide (KOH) breaks into potassium ions (K⁺) and hydroxide ions (OH^-).
• Hydrochloric acid (HCl) splits into hydrogen ions (H⁺) and chloride ions (Cl^-).

These ions are used to form the complete ionic equation, which gives a comprehensive view of the ions present during the reaction.

Balanced Chemical Equation

A balanced chemical equation is crucial as it shows that mass is conserved throughout the reaction, abiding by the Law of Conservation of Mass. For the reaction between potassium hydroxide (KOH) and hydrochloric acid (HCl), the balanced equation ensures that each type of atom appears the same number of times on both sides of the equation:

• The reactants are KOH(aq) and HCl(aq).
• The products are KCl(aq) and H₂O(l).

The balanced formula, which is the same in all conditions, is presented as:\[\text{KOH(aq) + HCl(aq) → KCl(aq) + H}_2 \text{O(l) }\] This equation confirms that one mole of KOH reacts with one mole of HCl to form one mole of KCl and water.

Net Ionic Equation

The net ionic equation is a simplified version of the complete ionic equation. It highlights only those ions and molecules undergoing a change. Spectator ions, which remain unchanged, are excluded.In the case of potassium hydroxide reacting with hydrochloric acid, the spectator ions are:

• Potassium ion (K⁺)
• Chloride ion (Cl^-)

Thus, the net ionic equation focuses solely on:\[\text{H}^+\text{(aq)} + \text{OH}^-\text{(aq)} \rightarrow \text{H}_2\text{O(l)} \] This equation tells us that hydrogen ions and hydroxide ions combine to form water, emphasizing the main change in the reaction.

Potassium Hydroxide

Potassium hydroxide (KOH) is a strong base commonly used in neutralization reactions. In its aqueous form, it dissociates completely into potassium ions (K⁺) and hydroxide ions (OH^-), which react readily with acids. Key characteristics of KOH:

• Strong electrolyte: Fully ionizes in water.
• Used in industries: Soap making, chemical manufacturing.
• Highly corrosive: Handle with care.

In neutralization, KOH reacts with acids like hydrochloric acid to form salts and water, making it a vital component of chemical reactions aimed at achieving a neutral pH.

Hydrochloric Acid

Hydrochloric acid (HCl) is a strong acid that dissociates completely in water to form hydrogen ions (H⁺) and chloride ions (Cl^-). It's widely used in various laboratory and industrial processes. Essential points about HCl:

• Strong electrolyte: Fully ionizes in aqueous solution.
• Commonly used: Cleaning, food processing, and metal refining.
• Corrosive nature: Should be handled carefully.

In a neutralization reaction with bases like potassium hydroxide, it reacts to form water and salts, thereby reducing the acidity and achieving neutrality in the process.