Question

Which of the following statements is incorrect in the context of silicones? (1) They are more stable to heat than other polymers. (2) The Si-O bond energy is high. (3) They are strongly water- repellent, are good elec trical insulators, and have nonsticking and anti forming properties. (4) The Si \(-\mathrm{O}\) bond energy is low. (a) \(1,2,4\) (b) \(1,2,3\) (c) \(2,3,4\) (d) 2,4

Short answer

The incorrect statements are in option (d) 2, 4.

Step-by-step solution

Read the Statements Carefully

Begin by reviewing all the given statements that are related to silicones. Understand the content and context of each statement to identify key concepts.

Understand Basic Properties of Silicones

Silicones are known for their heat stability, water repellency, good electrical insulation, nonstick properties, and antifouling abilities. This context will help assess the truthfulness of each statement.

Analyze Statement 1

Statement 1 claims that silicones are more stable to heat than other polymers. This is typically true for silicones due to the strong Si-O bond, contributing to their thermal stability.

Evaluate Statement 2

Statement 2 says the Si-O bond energy is high. This is correct as the strength of Si-O bonds contributes to the stability and robustness of silicone polymers.

Consider Statement 3

Statement 3 mentions silicones are water-repellent, good electrical insulators, and have non-sticking and anti-forming properties. This is accurate and matches known characteristics of silicones.

Examine Statement 4

Statement 4 implies the Si-O bond energy is low. This contradicts what is known (from statement 2), as the Si-O bond energy is high, marking this statement as incorrect.

Identify the Incorrect Statements

Now, cross-reference the incorrect statement(s) with the given answer choices: Statement 4 is incorrect. Hence, examine which answers include statement 4.

Key concepts

Si-O Bond Energy

Silicones are polymers consisting of repeating units of siloxane, a compound comprised of silicon and oxygen atoms often combined with carbon and hydrogen. The Si-O bond forms the backbone of these silicone structures. Typically, the energy of the Si-O bond is significantly high, at approximately 452 kJ/mol. This strong bond energy is due to the robust interactions between silicon and oxygen, which make it among the strongest single bonds found in organic chemistry.

• Strength: High Si-O bond energy contributes to silicones' overall stability, making them more resistant to breaking under chemical reactions and physical stress.
• Resilience: The bond's tenacity is pivotal in sustaining the material's structural integrity.

Understanding this bond's power helps explain the robustness of silicone materials in various applications, from kitchenware to insulation.

Properties of Silicones

Silicones come with a set of remarkable properties that distinguish them from other polymer materials. These properties not only enhance their functionality but also expand their usability in numerous industrial and everyday applications.

• Water Repellency: Due to their hydrophobic nature, silicones form barriers against water, helping to protect surfaces from moisture.
• Electrical Insulation: Silicones are excellent insulators, making them ideal for use in electronic components where electricity must be managed or contained.
• Non-Stick Nature: They do not easily bond with other substances, giving them anti-sticking and antifouling characteristics. This makes cleaning easy, especially in kitchen applications.

These unique properties of silicones make them invaluable in industries ranging from automotive to medicine.

Thermal Stability of Silicones

Silicones are particularly noted for their exceptional thermal stability. Their ability to maintain stability under exposure to high temperatures is a direct result of the strong Si-O bond energy. Even when subjected to drastic thermal environments, the silicone matrix remains largely unaffected, unlike many other polymers that may degrade or lose structural integrity.

• Resistance to Heat: Silicones can usually withstand temperatures ranging from -100°C to +200°C and in special cases even higher, without losing their elastic properties.
• Durability: This unique thermal resilience makes silicones suitable for use in environments where heat resistance is critical, such as automotive engines and cooking applications.

The thermal stability of silicones also reduces the risk of spontaneous ignition and the emission of toxic gases under heat, ensuring safety in their widespread applications.