Problem 16 - A Complete Resource Book in Chemistry for JEE Main

Question

Which method is used for the separation of two immiscible liquids? (a) chromatography (b) fractionating column (c) separating funnel(d) fractional distillation

Step-by-Step Solution

Answer

The method used is a separating funnel (c).

Step 1: Understanding the Problem

We need to determine which method is best suited for separating two immiscible liquids. Immiscible liquids do not mix together and typically form distinct layers when combined.

Step 2: Evaluating Option A: Chromatography

Chromatography is a method used to separate mixtures of substances, typically dissolved in a solvent, based on different rates of movement through a medium. It is not suited for separating immiscible liquids.

Step 3: Evaluating Option B: Fractionating Column

A fractionating column is used in distillation to separate mixtures based on different boiling points. While it can separate liquids, it is more complex than necessary for just separating immiscible liquids.

Step 4: Evaluating Option C: Separating Funnel

A separating funnel is specifically designed for separating two immiscible liquids. It takes advantage of their density differences, allowing one liquid to be drained from another.

Step 5: Evaluating Option D: Fractional Distillation

Fractional distillation is used to separate a mixture into individual components based on differences in boiling points, not suited for immiscible liquids which do not mix together.

Step 6: Conclusion

The separating funnel is the most appropriate tool for separating two immiscible liquids.

Key Concepts

Immiscible Liquids

Immiscible liquids are two or more liquids that do not mix together, forming distinct layers instead. Imagine oil and water. Mix them, and you'll see the oil floats on top, refusing to blend. This happens because the molecules in the liquids don't attract. Instead, they repel each other due to different properties such as polarity. Polarity refers to how electrical charge is distributed in a molecule. For instance, water is polar, while oil is non-polar.

• Polar molecules like water attract each other but repel non-polar molecules, like oil.
• This repulsion causes the layers to form when immiscible liquids are combined.

Understanding this fundamental concept is crucial because it forms the basis for the separation techniques used in labs and industries.

Separating Funnel

A separating funnel is a laboratory tool used specifically for separating immiscible liquids. This method uses gravity and density differences between the liquids.
It's a simple yet effective process:

• The mixture is placed into the funnel, and the denser liquid settles at the bottom.
• Opening a stopcock at the bottom allows the denser liquid to be drained off first.

After draining the first layer, the stopcock is closed, leaving the lighter liquid inside. This tool is specifically for immiscible liquids, allowing clear separation without needing complex procedures or equipment. It's highly favored for its simplicity and efficiency in the lab.

Fractional Distillation

Fractional distillation is a process used to separate a mixture into fractions based on differences in boiling points. It's perfect for miscible liquids that are mixed together, unlike immiscible liquids. Here's a quick rundown of how it works:

• Heat is applied to the mixture, causing the liquid with the lowest boiling point to vaporize first.
• The vapor then rises through a fractionating column, cools, and condenses back into a liquid.

This method is commonly used in the production of alcohol and the separation of crude oil into gasoline and other products. While fractional distillation is an excellent method for separating certain types of liquid mixtures, it is not used for immiscible liquids that are already in separate layers.

Chromatography

Chromatography is a versatile technique used to separate different components in a mixture. Unlike methods focused on immiscible liquids, chromatography is often used for solutions where substances are dissolved and need to be separated based on how they move through another material.

• A single phase, such as a thin layer of absorbent paper or a column with a special packing, is employed.
• When the mixture passes through, individual components travel at unique rates based on their interaction with the material, thus separating them.

It's not applicable for immiscible liquids, which naturally separate; however, chromatography excels in separating colored compounds, simplifying complex mixtures into individual substances, like separating different pigments in inks and dyes.