Question

CO\(_2\) is a gas, while SiO\(_2\) is a solid, but both are

• A. acidic
• B. ionic
• C. discrete molecules
• D. covalent containing \(\pi\)-bonds

Hint:

Acidic oxides react with bases to form salts.

Answer 1

The Correct Option is A

To determine why CO₂ is a gas while SiO₂ is a solid, yet both are categorized as acidic, we must examine the nature of their bonding and molecular structure.

1. Both CO₂ and SiO₂ are composed of non-metals and are primarily covalent in nature. However, the physical state of a compound is dependent on its molecular structure and intermolecular forces.
2. CO₂ (Carbon Dioxide):
   • CO₂ consists of discrete molecules held together by weak Van der Waals forces, which allows it to exist as a gas at room temperature.
   • CO₂ has a linear molecular geometry with a central carbon atom double-bonded to two oxygen atoms, resulting in a stable configuration through covalent bonding with \(\pi\)-bonds.
   • It reacts with water to form carbonic acid, demonstrating its acidic nature: 

\[\text{CO}_2 + \text{H}_2\text{O} \rightarrow \text{H}_2\text{CO}_3\]

1. SiO₂ (Silicon Dioxide):
   • SiO₂ forms a giant covalent (network) solid, where each silicon atom is covalently bonded to four oxygen atoms, forming a three-dimensional network.
   • This structure results in strong bonds throughout the material, giving SiO₂ a high melting point and a solid state at room temperature.
   • SiO₂ exhibits acidic behavior as it can react with bases to form silicates:
2. Conclusion: Both CO₂ and SiO₂ are acidic due to their ability to react with water or bases to form acids or salts, respectively. Despite their differences in physical state, the correct answer is acidic. Both compounds exhibit non-metallic properties and form covalent bonds, but it is their acidic nature that is the common characteristic being examined.