Problem 10 - Chemical Principles: The Quest for Insight

Question

Use the periodic rable to determine which oxides form acidic solutions in water and which form basic solutions: (a) \(\mathrm{P}_{4} \mathrm{O}_{105}\) (b) \(\mathrm{Na}_{2} \mathrm{O}\); (c) \(\mathrm{CO}_{2}\); (d) \(\mathrm{MgO}\).

Step-by-Step Solution

Answer

\((a) \mathrm{P}_{4} \mathrm{O}_{10} - Acidic, (b) \mathrm{Na}_{2} \mathrm{O} - Basic, (c) \mathrm{CO}_{2} - Acidic, (d) \mathrm{MgO} - Basic.

Step 1: Understanding Acidity and Basicity of Oxides

Oxides of nonmetals typically form acidic solutions in water, while oxides of metals usually form basic solutions.

Step 2: Classifying \(\mathrm{P}_{4} \mathrm{O}_{10}\)

Use the periodic table to identify phosphorus (P) as a nonmetal. Thus, \(\mathrm{P}_{4} \mathrm{O}_{10}\) forms acidic solutions in water.

Step 3: Classifying \(\mathrm{Na}_{2} \mathrm{O}\)

Sodium (Na) is a metal. Consequently, \(\mathrm{Na}_{2} \mathrm{O}\) forms basic solutions in water.

Step 4: Classifying \(\mathrm{CO}_{2}\)

Carbon (C) is a nonmetal, so carbon dioxide, \(\mathrm{CO}_{2}\), forms acidic solutions in water.

Step 5: Classifying \(\mathrm{MgO}\)

Magnesium (Mg) is a metal. Therefore, \(\mathrm{MgO}\) forms basic solutions in water.

Key Concepts

Periodic Table

The periodic table is not just a collection of elements; it's a map of chemical characteristics, including acidity and basicity. Each element is placed based on its atomic number, electron configuration, and recurring chemical properties.

On one side of the periodic table, you have nonmetals, which tend to share electrons or gain them from metals. These elements are key players in forming oxides that, when dissolved in water, create acidic solutions. On the other side, you find metals which have a propensity to lose electrons easily, thus forming oxides that usually produce basic solutions in water. Understanding the organization of the periodic table helps us predict the type of oxides an element will form.

Acidic Solutions in Water

When certain oxides dissolve in water, they react to form acidic solutions, which have a pH less than 7. Acidity in water is often a result of nonmetal oxides, like sulfur dioxide or carbon dioxide, reacting with H2O to form corresponding acids. For instance, carbon dioxide reacts with water to form carbonic acid, lending the solution its acidic nature.

These reactions are crucial for understanding environmental phenomena, such as acid rain, and have wide-ranging implications in chemistry, from industrial processes to biological systems.

Basic Solutions in Water

Opposite to acidic solutions, some oxides form basic solutions when dissolved in water, characterized by a pH greater than 7. These are typically metal oxides, like sodium oxide or magnesium oxide. When these substances interact with water, they produce metal hydroxides, which confer the solution its basic properties.

For example, when sodium oxide dissolves in water, it forms sodium hydroxide, a strong base. These reactions are not only important in laboratories but also have practical applications, such as in soap making or water treatment.

Chemical Properties of Oxides

Oxides are compounds formed by the combination of oxygen with another element. Their chemical properties, such as acidity or basicity, are largely dependent on the nature of the other element involved in their formation.

Nonmetal oxides tend to form acidic aqueous solutions, often acting as acid anhydrides, meaning they can form acids when combined with water. On the other hand, metal oxides typically act as basic anhydrides, forming metal hydroxides when reacting with water. Understanding these properties helps chemists to manipulate reactions for desired outcomes and is fundamental for a wide range of scientific and industrial applications.