Question

Which from following statements is correct regarding a detergent sodium lauryl sulphate?

• A. It is anionic detergent and is used in toothpaste.
• B. It is cationic detergent and is used as household detergent.
• C. It is cationic detergent and is used as hair conditioner.
• D. It is an ether and used as liquid detergent.

Hint:

Anionic detergents like Lauryl Sulphate are common in toothpaste. Cationic detergents (like Cetyltrimethylammonium bromide) are usually in hair conditioners.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Synthetic detergents are broadly classified into three categories—anionic, cationic, and non-ionic—based on the electrical charge carried by their hydrophilic (water-loving) head group. Sodium lauryl sulphate is a ubiquitous synthetic detergent, and knowing its classification helps deduce its common uses.
Step 2: Key Formula or Approach:
Approach: Analyze the chemical structure and name of sodium lauryl sulphate to determine its ionic nature upon dissociation, and then relate this to standard commercial applications.
Step 3: Detailed Explanation:
The chemical formula for sodium lauryl sulphate (often abbreviated as SLS or SDS) is $\text{CH}_3(\text{CH}_2)_{11}\text{OSO}_3^-\text{Na}^+$. When dissolved in an aqueous solution, it dissociates completely into a long-chain alkyl sulphate anion ($\text{CH}_3(\text{CH}_2)_{11}\text{OSO}_3^-$) and a sodium cation ($\text{Na}^+$). Because the actual cleansing action is performed by the large, negatively charged anionic part of the molecule, it is formally classified as an anionic detergent. Anionic detergents are highly effective and are widely utilized for general household cleaning. More specifically, sodium lauryl sulphate is a very common foaming agent and surfactant used in personal care products, particularly in toothpastes and shampoos, to create a rich lather. Let's evaluate the given options based on these facts: - (A) Correctly identifies it as an anionic detergent and notes its widespread use in toothpaste. - (B) Incorrectly identifies it as a cationic detergent. - (C) Incorrectly identifies it as cationic (cationic detergents, such as cetyltrimethylammonium bromide, are typically used in hair conditioners). - (D) Incorrectly identifies its functional group as an ether; it is chemically a sulfate ester salt.
Step 4: Final Answer:
Sodium lauryl sulphate is an anionic detergent and is used in toothpaste.