Problem 11 - Chemistry and Chemical Reactivity

Question

Place the following oxides in order of increasing basicity: \(\mathbf{C O}_{2}, \mathrm{SiO}_{2}, \mathrm{SnO}_{2}\).

Step-by-Step Solution

Answer

The order is: CO2 < SiO2 < SnO2.

Step 1: Understand Basicity in Oxides

Basicity of oxides refers to the oxide's ability to react with acids to form salts and water. Generally, basicity increases as we move down a group in the periodic table and decreases as we move right across a period.

Step 2: Analyze Carbon Dioxide ( CO2)

Carbon dioxide is a well-known acidic oxide. It's a common component of the air and forms carbonic acid when dissolved in water. Hence, it has low basicity.

Step 3: Analyze Silicon Dioxide ( SiO2)

Silicon dioxide, or silica, is typically considered weakly acidic and does not readily react with acids or bases. It has a slightly higher basicity than CO2, but it's mainly amphoteric depending on conditions.

Step 4: Analyze Tin(IV) Oxide ( SnO2)

Tin(IV) oxide is also amphoteric, meaning it can react with both acids and bases. However, being a metallic oxide, it generally has higher basicity than silicon dioxide and carbon dioxide.

Step 5: Rank the Oxides

Based on the analysis, the order of increasing basicity is: 1. CO2, 2. SiO2, 3. SnO2.

Key Concepts

Periodic Table Trends

The periodic table is a treasure map of chemical properties that helps us predict how elements and their compounds behave. When discussing the basicity of oxides, it's crucial to understand periodic table trends.
Basicity refers to the ability of an oxide to neutralize an acid. In essence, basicity is synonymous with how readily an oxide can form a base when combined with water.

• As we move down a group (column) in the periodic table, elements tend to become more metallic. This shift often increases the basicity of their oxides.
• Conversely, when moving across a period (row) from left to right, elements become less metallic and more non-metallic, typically decreasing oxide basicity.

These trends help us predict that oxides of elements on the left and lower part of the periodic table are generally more basic than those on the top right, such as carbon dioxide \(CO_2\). Understanding these trends offers clues about the properties of different oxides, assisting in problem-solving tasks like ranking them by basicity.

Amphoteric Oxides

Amphoteric oxides are fascinating because they can behave as either acidic or basic, depending on the reaction partner. This dual-behavior stems from their unique composition and position in the periodic table.
Amphoteric nature means an oxide can react with both acids and bases. For example, Tin(IV) oxide \(SnO_2\) is an amphoteric oxide. In acidic conditions, it can act as a base, whereas in basic conditions, it behaves like an acid.

• Being amphoteric, \(SnO_2\) shows a more pronounced basic character compared to strictly acidic oxides like carbon dioxide \(CO_2\).
• Silicon dioxide \(SiO_2\) is another example and exhibits weakly acidic to amphoteric behavior based on conditions, making it unique but primarily non-reactive under standard conditions.

Amphoteric oxides like \(SnO_2\) and \(SiO_2\) are important in various industrial applications due to their ability to neutralize different types of substances with their dual reactivity.

Acidic Oxides

Acidic oxides are oxides that form acids when combined with water. These oxides, typically formed from nonmetals, easily react with water to produce acidic solutions.
Carbon dioxide \(CO_2\) is a textbook example of an acidic oxide. When dissolved in water, \(CO_2\) forms carbonic acid \(H_2CO_3\), accentuating its acidic nature.

• Acidic oxides often stem from elements positioned towards the top-right corner of the periodic table.
• These oxides usually form bonds with nonmetals, contributing to their acidic behavior.

Understanding the behavior of acidic oxides like \(CO_2\) is essential, especially in environmental contexts where \(CO_2\) influences phenomena like ocean acidification. Recognizing that acidic oxides represent one extreme on a spectrum of oxide reactivity helps in comparing them with amphoteric and basic oxides.