Coffee stains can best be removed by?

Analysis

The question asks for the most effective substance to remove coffee stains from fabrics or surfaces. Coffee stains are primarily organic in nature, containing tannins and other plant-based pigments.

Concept Explanation

To remove stains, you must use a substance that can either dissolve the stain (a solvent) or chemically break it down (a cleaning agent).

• Kerosene and Turpentine: These are non-polar organic solvents. They are excellent for removing oil-based stains like grease, paint, or wax, but they are ineffective against water-soluble stains like coffee.
• Ammonia solution: While ammonia is a common household cleaner, it is highly alkaline and can damage certain fabrics or cause color bleeding.
• Borax (Sodium tetraborate): Borax acts as a mild alkali and a bleaching agent. When dissolved in water, it helps to break down the complex organic molecules found in coffee, making them water-soluble and easier to wash away without damaging the fabric.

Step-by-Step Solution

1. Identify the nature of the stain: Coffee is a water-based, organic stain.
2. Evaluate the solvents: • Kerosene and Turpentine are non-polar; they will not mix with the water-based coffee stain. • Ammonia is a strong base that is often too harsh for delicate fabrics.
3. Evaluate the cleaning agent: Borax is a salt of boric acid. In water, it creates a slightly alkaline solution that effectively lifts organic pigments (tannins) from fibers. It is widely recognized in home economics and chemistry for its ability to remove stubborn organic stains like coffee, tea, and wine.

Conclusion

Based on chemical properties and standard cleaning practices, a solution of borax in water is the most effective and safe method for removing coffee stains among the given options.

Exam Tip: When dealing with "stain removal" questions in Chemistry, always categorize the stain first:

• Oil/Grease: Use organic solvents (Kerosene, Turpentine, Petrol).
• Water-based/Organic (Coffee, Tea, Ink): Use mild alkalis or oxidizing agents (Borax, Hydrogen peroxide, or mild detergents).