Question

This section contains multiple choice questions. Each question has 4 choices (a), (b), (c) and (d), out of which ONLY ONE is correct. Arrange the following in the increasing order of their intermolecular forces nylon, PVC, rubber, cellulose nitrate (B) (DI (a) \((\mathrm{C})<(\mathrm{A})<(\mathrm{B})<(\mathrm{D})\) (b) \((\mathrm{C})<(\mathrm{B})<(\mathrm{A})<(\mathrm{D})\) (c) \((\mathrm{D})<(\mathrm{C})<(\mathrm{B})<(\mathrm{A})\) (d) \((\mathrm{D})<(\mathrm{C})<(\mathrm{A})<(\mathrm{B})\)

Short answer

Question: Arrange the following materials in the increasing order of their intermolecular forces: nylon, PVC, rubber, and cellulose nitrate. Answer: (b) PVC < Rubber < Nylon < Cellulose nitrate

Step-by-step solution

Identify the intermolecular forces in each material

First, we need to identify the types of intermolecular forces present in each material. 1. Nylon has hydrogen bonds as well as van der Waals forces 2. PVC (polyvinyl chloride) mainly has van der Waals forces 3. Rubber also has primarily van der Waals forces 4. Cellulose nitrate has hydrogen bonds and ionic interactions.

Compare the strength of intermolecular forces

Now, we need to compare the strength of the intermolecular forces present in each material. Generally, hydrogen bonds are stronger than van der Waals forces, and ionic interactions are the strongest among the three. Based on this, we can deduce the order of their intermolecular forces strength: PVC < Rubber < Nylon < Cellulose nitrate.

Match the order with the given options

Now, we have to find the option that matches our determined order. Using the given options A, B, C, and D as (A) - nylon, (B) - PVC, (C) - rubber, and (D) - cellulose nitrate, we find that our order matches with: \((\mathrm{C})<(\mathrm{B})<(\mathrm{A})<(\mathrm{D})\) Hence, the correct answer is (b).

Key concepts

Hydrogen Bonds

Hydrogen bonds are a type of intermolecular force that occur when hydrogen is bound to a highly electronegative atom, such as oxygen, nitrogen, or fluorine. This bond is primarily due to the attraction between the slightly positive charge of the hydrogen atom and the slightly negative charge on the electronegative atom nearby. In simpler terms, hydrogen bonds are like strong magnets that hold molecules together.

For example, in water (\( H_2O \)), each molecule is bonded to another by hydrogen bonds, explaining water's high boiling point compared to other similar molecules. These bonds are stronger than most other non-covalent interactions because of the high polarity involved.

• Characteristic: Hydrogen bonds are directional, meaning their strength depends heavily on the angle between the bonded atoms.
• Strength: They are stronger than van der Waals forces but weaker than ionic interactions.

Nylon and cellulose nitrate exhibit hydrogen bonding. In nylon, the presence of hydrogen bonds contributes to its significant tensile strength making it a popular choice in the textile industry.

Van der Waals Forces

Van der Waals forces are the weakest type of intermolecular forces, yet are crucial for the interaction between all molecules. This force arises from induced electrical interactions between two or more atoms or molecules that are very close to each other.

These forces are generally divided into three types:

• Dispersion forces (London forces) are present between all atoms and molecules, regardless of their polarity. They occur due to random temporary changes in electron density.
• Dipole-dipole interactions occur between polar molecules where the positive end of one molecule is attracted to the negative end of another.
• Dipole-induced dipole interactions occur when a polar molecule induces a dipole in an otherwise nonpolar molecule.

Rubber and PVC are primarily held together by van der Waals forces. Because these forces are relatively weak, materials like rubber can stretch easily, giving them elastic properties. Although not very strong, van der Waals forces are abundant and can accumulate to give notable effects in large collections of molecules, like in polymers.

Ionic Interactions

Ionic interactions are among the strongest types of intermolecular forces. They occur between positively charged cations and negatively charged anions. Think of them as the force that holds a magnet to a fridge door but on a microscopic scale.

The strength of ionic interactions makes them critical in many biological and chemical systems. For instance, salt (\( NaCl \)), is a collective solid structure formed from such interactions.

• Durability: Ionic bonds are very stable in the solid state but can dissolve in water, breaking down into individual ions.
• Strength: Ionic interactions are stronger than hydrogen bonds and much stronger than van der Waals forces.

Cellulose nitrate displays ionic interactions, which contribute to its stability and rigidity. This strength is why cellulose nitrate is used for making strong, durable materials like celluloid.Each of these forces contributes to the behavior of materials, dictating their boiling points, melting points, and elasticity, and their understanding is crucial to the field of material science.