Problem 69 - A Complete Resource Book in Chemistry for JEE Main

Question

The best solvent for removing butter stain from cloth is (a) \(\mathrm{H}_{2} \mathrm{O}\) (b) \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\) (c) \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OC}_{2} \mathrm{H}_{5}\) (d) \(\mathrm{CHCl}_{3}\)

Step-by-Step Solution

Answer

(d) \( \mathrm{CHCl}_{3} \) is the best solvent for removing butter stains.

Step 1: Understanding the Nature of Butter

Butter is a type of fat, which is a non-polar substance. Therefore, it will dissolve more efficiently in non-polar solvents due to the principle of 'like dissolves like'.

Step 2: Analyzing the Options

We have to choose the most suitable solvent for removing butter stains from the given options: (a) \(H_{2} O\), a highly polar solvent.(b) \(C_{2} H_{5} OH\), which is partially polar and partially non-polar.(c) \(C_{2} H_{5} OC_{2} H_{5}\), which is an ether and primarily non-polar.(d) \(CHCl_{3}\), a non-polar solvent.

Step 3: Matching Solvent Polarity with Stain

Since butter is non-polar, the best solvent to remove it will likely be a non-polar solvent. \(C_{2} H_{5} OC_{2} H_{5}\) and \(CHCl_{3}\) are both non-polar, but \(CHCl_{3}\) is more effective for dissolving fats.

Step 4: Selecting the Best Solvent

Among the options, \(CHCl_{3}\) is the most effective non-polar solvent that can dissolve and remove butter better than the other solvents listed.

Key Concepts

Non-Polar Solvents

When trying to remove stains, it's often crucial to match the nature of the stain with the properties of the solvent. This is where non-polar solvents come into play. Non-polar solvents are known for their ability to dissolve non-polar substances like fats and oils.
What does it mean when we call a solvent non-polar? This term refers to the lack of a significant difference in electronegativity across the molecules that make up the solvent. In simpler terms, non-polar molecules do not have charged ends, and their electrons are shared fairly equally.
In the context of our problem, solvents like chloroform (\(CHCl_3\)) and diethyl ether (\(C_2H_5OC_2H_5\)) are categorized as non-polar. These solvents are particularly effective at dissolving substances like butter, which is itself non-polar due to the fatty acids it contains.

Like Dissolves Like

The phrase "like dissolves like" is key in chemistry and refers to the tendency of solvents to dissolve solutes with similar polarity. In simple terms, polar solvents dissolve polar substances, and non-polar solvents dissolve non-polar substances.
This is important because the effectiveness of a solvent is largely determined by this compatibility. For example:

• Water (\(H_2O\)), being polar, dissolves salts and sugars which are also polar.
• Chloroform (\(CHCl_3\)), being non-polar, is great for dissolving oils and fats, which are non-polar.

Thus, using a non-polar solvent like chloroform is ideal for removing butter stains because it can effectively interact with and dissolve the fats in butter.

Dissolution of Fats

Understanding how fats dissolve will help clarify why non-polar solvents are so effective for this purpose. Fats consist of long chains of hydrocarbons, which are mainly non-polar due to their symmetrical structure and lack of distinct positive or negative poles.
When a non-polar solvent is applied to fats, the non-polar molecules of the solvent interact with the non-polar hydrocarbon chains of the fat through van der Waals forces. These interactions allow the solvent molecules to surround and separate the fat molecules, leading to the dissolution of fats.
For practical purposes, choosing an effective non-polar solvent, like chloroform, can greatly enhance the ability to remove greasy stains or residues. By leveraging the principle of 'like dissolves like,' it's possible to identify the most efficient cleaning agents for non-polar substances.