Problem 21 - Chemistry and Chemical Reactivity

Question

Write a balanced equation for the ionization of nitric acid in water.

Step-by-Step Solution

Answer

HNO₃ (aq) → H⁺ (aq) + NO₃⁻ (aq).

Step 1: Identify the Reaction Components

Nitric acid (HNO₃) is a strong acid, and when it is dissolved in water, it completely ionizes into hydrogen ions (H⁺) and nitrate ions (NO₃⁻). We need to represent this reaction as it occurs in aqueous solution.

Step 2: Write the Chemical Equation

The chemical reaction for the ionization of nitric acid in water can be written as: \[ \text{HNO}_3 (aq) \rightarrow \text{H}^+ (aq) + \text{NO}_3^- (aq) \] This equation shows that a molecule of nitric acid dissociates completely to form one hydrogen ion and one nitrate ion.

Step 3: Balance the Equation

In this case, the equation is already balanced as there is one molecule of HNO₃ producing one H⁺ ion and one NO₃⁻ ion. The number of each type of atom is equal on both sides of the equation.

Key Concepts

Chemical Equation

A chemical equation is a symbolic representation of a chemical reaction. It shows how reactants are transformed into products. In the case of acid-base reactions, this often involves the transfer of protons (H⁺). For nitric acid ionization, the equation illustrates the conversion:

• The reactant, nitric acid (HNO₃), on the left side, dissociates.
• The products, hydrogen ions (H⁺) and nitrate ions (NO₃⁻), appear on the right side.

This equation not only shows the substances involved but also conveys their phase - 'aq' to denote they are in an aqueous solution. Visible coefficients are used to balance the equation, ensuring the number of atoms for each element is conserved, though in this case, the equation is naturally balanced.

Ionization

Ionization is the process where a molecule breaks into ions when dissolved in water. Nitric acid, being a strong acid, ionizes completely:

• It releases a hydrogen ion (H⁺).
• The remaining nitrogen and oxygen atoms form a nitrate ion (NO₃⁻).

In the ionization of nitric acid, each molecule splits into two ions:
\[\text{HNO}_3 \rightarrow \text{H}^+ + \text{NO}_3^- \]This process is fundamental in understanding how acids interact in aqueous environments, influencing their chemical properties and reactions.

Strong Acid

A strong acid is characterized by its complete ionization in water. Nitric acid (HNO₃) is a prime example:

• It completely dissociates into its ions in an aqueous solution.
• There are no intact molecules left; all form H⁺ and NO₃⁻.

This total ionization implies:
- High hydrogen ion concentration in its solution, leading to low pH.
The full dissociation makes strong acids highly effective in proton transfer reactions, a key aspect in many chemical processes.

Aqueous Solution

An aqueous solution is one where water is the solvent. In chemistry, many reactions occur in this medium due to water's ability to dissolve various substances. For nitric acid:

• It's dissolved in water, indicated by the '(aq)' in the equation.
• This dissolution allows it to ionize completely, enhancing reactivity.

Aqueous solutions facilitate reactions by allowing ions to move and interact freely, crucial for the function of acids in both biological and chemical contexts. Understanding this helps students grasp why water is such a vital medium for chemical reactions.