Problem 189 - A Complete Resource Book in Chemistry for JEE Main

Question

The volume of a colloidal particle, \(\mathrm{V}_{\mathrm{c}}\) as compared to the volume of a solute particle in a true solution \(\mathrm{V}\). could be [2005] (a) \(\sim 1\) (b) \(\sim 10^{23}\) (c) \(\sim 10^{-3}\) (d) \(\sim 10^{3}\)

Step-by-Step Solution

Answer

The volume of a colloidal particle is about 1000 times that of a solute particle, so the answer is (d) \( \sim 10^{3} \).

Step 1: Understanding colloidal and true solutions

A colloidal particle is much larger than solute particles in a true solution. In this exercise, we're exploring how large this difference in volume can be.

Step 2: Comparing particle sizes

Colloidal particles are typically in the range of 1 nm to 1000 nm, while solute particles (like ions or small molecules) in true solutions are usually at the atomic or molecular level, ranging from 0.1 nm to 1 nm.

Step 3: Calculating the approximate size ratio

Assuming a rough estimate where the colloidal particle is 10 times larger than the solute particle in each dimension (length, width, height), the volume ratio becomes \[ \text{Volume Ratio} = (\text{Size Ratio})^3 = 10^3. \] This results from the volume formula \( V = \text{length} \times \text{width} \times \text{height} \).

Step 4: Selecting the appropriate answer

Given our calculation that the volume of a colloidal particle is about \( 10^{3} \) times the volume of a solute particle, the correct answer is option (d).

Key Concepts

Volume Ratio

When discussing the differences between colloidal particles and solute particles in true solutions, the concept of volume ratio plays a critical role. Volume ratio refers to the comparison of the volume of one type of particle to another.

In a simple analogy, consider comparing a giant beach ball (colloidal particle) to a small marble (solute particle). Mathematically, this volume ratio can be described if we assume that every dimension of the colloidal particle is 10 times larger than the solute particle.

• This results in a volume ratio expressed as \( 10^3 \) or 1000, derived from \( 10 imes 10 imes 10 \), reflecting each dimension.
• The large magnitude of this number shows just how much larger colloidal particles can be compared to solute particles.

Understanding this volume ratio is important as it heavily influences the behavior and properties of colloidal solutions, such as their ability to scatter light, which is a characteristic phenomenon called the Tyndall effect.

Colloidal Particles

Colloidal particles are fascinating because they exist in a size realm somewhere between true molecular solutions and suspensions. These particles measure between 1 nm and 1000 nm.

To visualize this, consider a fog or a mist, where the particles are not small enough to dissolve like sugar in water but not too large to settle out like sand in a glass. Colloids are dispersed throughout another substance evenly, distinguishing them from suspensions, where particles eventually settle out over time.

• The unique size of colloidal particles enables them to display properties not seen in other mixtures, such as Brownian motion—a random movement due to collisions with surrounding molecules.
• Their surface area relative to volume is quite high, impacting reactivity and stability.

This capability to stay uniformly distributed is essential for applications ranging from food production to pharmaceuticals. Indeed, understanding colloidal particles helps in numerous scientific innovations.

True Solutions

In the realm of chemistry, true solutions represent a type of homogeneous mixture where a solute is completely dissolved in a solvent. The particle size in a true solution is typically at the molecular or ionic level, usually less than 1 nm.

Imagine adding salt to water: the salt particles dissolve entirely, becoming invisible, and leave no residue behind. This complete dissolution is a hallmark of true solutions and distinguishes them from other mixture types.

• Due to their small size, solute particles in a true solution do not scatter light, making the Tyndall effect absent, unlike with colloids.
• True solutions appear clear and uniform, with no discernible difference between the solute and the solvent particles to the naked eye.

From everyday applications like saltwater to more complex solutions in chemical manufacturing, true solutions have pivotal roles across various fields. Recognizing and differentiating them from colloidal solutions help in activities such as purification, chemical reactions, and material science.