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) \(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{OC}_{2} \mathrm{H}_{5}\) (d) \(\mathrm{CHCl}_{3}\)

Step-by-Step Solution

Answer

Chloroform (d) is the best solvent for butter stains.

Step 1: Understanding the Properties of Butter

Butter is a lipid, which means it is nonpolar and consists of a mix of fats. This property must be considered when choosing a solvent because like dissolves like; nonpolar substances are best dissolved by nonpolar solvents.

Step 2: Assessing the Solvents

To determine which solvent is best for removing butter, we need to know whether each solvent is polar or nonpolar: - (a) \(\mathrm{H_{2}O}\): Water is polar.- (b) \(\mathrm{C_{2}H_{5}OH}\): Ethanol is polar.- (c) \(\mathrm{C_{2}H_{3}OC_{2}H_{5}}\): Ethyl acetate is slightly polar but can dissolve some nonpolar substances due to its ester group.- (d) \(\mathrm{CHCl_{3}}\): Chloroform is nonpolar.

Step 3: Matching Solvent to Butter Properties

Since butter is nonpolar, the best solvents for removing it would be nonpolar or weakly polar solvents. Between the options, ethyl acetate and chloroform are better suited than water and ethanol. However, chloroform is especially nonpolar, making it a prime candidate.

Step 4: Selection of the Best Solvent

Given that chloroform (\(\mathrm{CHCl_{3}}\)) is highly nonpolar, it is the best solvent for removing a butter stain from cloth, as it will more effectively dissolve the butter.

Key Concepts

Polarity

In chemistry, polarity refers to the distribution of electrical charge around atoms, molecules, or chemical groups. A polar substance has a region with slight positive charge and a region with slight negative charge. These charges occur because atoms in molecules share electrons unequally. The classic example is water (\(\mathrm{H_{2}O}\)), where the oxygen atom is more electronegative, pulling electrons towards itself and away from the hydrogen atoms. This gives water its "polar" characteristic.

• Polarity is crucial for understanding solubility.
• Polar substances typically dissolve other polar substances, while nonpolar substances dissolve nonpolar substances.
• This idea is known as "like dissolves like."

For students: Always consider the polarity of a compound when predicting how it interacts with another substance.

Nonpolar Solvents

Nonpolar solvents are substances that do not have a significant difference in electronegativity between their atoms, resulting in an even distribution of electrical charge. They do not possess poles of positive and negative charge. Because of this property, nonpolar solvents are excellent at dissolving other nonpolar substances, like oils and fats, which are commonly found in everyday items like food stains, cosmetics, and greases.

• Common examples include substances like chloroform (\(\mathrm{CHCl_3}\)) and hexane.
• Such solvents are often used in industrial applications and household cleaning products to remove nonpolar residues.

Important note: Nonpolar solvents can sometimes be hazardous, so always follow safety guidelines when using them.

Lipids

Lipids are a broad group of naturally occurring molecules that include fats, waxes, and oils. They are mostly nonpolar, which means they do not dissolve well in water, but they can dissolve in nonpolar solvents. This property is a result of their structure, which is mainly composed of long chains of hydrocarbons.

• Lipids play essential roles in biology as energy storage molecules, structural components of cell membranes, and signaling molecules.
• Their nonpolar nature means they can form waterproof barriers, contributing to skin protection and waterproof plant surfaces.

When dealing with stains from substances like butter, which is a lipid, using a nonpolar solvent is highly effective at breaking down the stain and removing it from materials.