NDA 2025
- Exam
- NDA
- Year
- 2025
- Subject
- General Ability
- Chapter
- General Science
NDA 2025 · General Ability · General Science
Which one of the following statements is NOT correct?
Which one of the following statements is NOT correct?
Options
- AThe molecules of soap are sodium or potassium salts of long chain fatty acids
- BThe molecules of soap contain both hydrophobic and hydrophilic ends
- CDetergents are more effective than soaps in hard water
- DIn micelles the ionic-end of the molecules is towards oil droplet while the other end faces outside
Correct answer
D. In micelles the ionic-end of the molecules is towards oil droplet while the other end faces outside
Step-by-step solution
Soap molecules are sodium or potassium salts of long chain fatty acids. They consist of two parts: a hydrophobic (water-repelling) hydrocarbon tail and a hydrophilic (water-attracting) ionic head.
In a micelle formed around an oil droplet, the hydrophobic hydrocarbon tails point inwards and dissolve in the oil droplet, while the hydrophilic ionic ends point outwards and interact with the surrounding water.
Therefore, the statement that the ionic end is towards the oil droplet and the other end faces outside is incorrect.
Detergents are more effective than soaps in hard water because they do not form insoluble precipitates (scum) with the calcium and magnesium ions present in hard water.
Answer: In micelles the ionic-end of the molecules is towards oil droplet while the other end faces outside
In a micelle formed around an oil droplet, the hydrophobic hydrocarbon tails point inwards and dissolve in the oil droplet, while the hydrophilic ionic ends point outwards and interact with the surrounding water.
Therefore, the statement that the ionic end is towards the oil droplet and the other end faces outside is incorrect.
Detergents are more effective than soaps in hard water because they do not form insoluble precipitates (scum) with the calcium and magnesium ions present in hard water.
Answer: In micelles the ionic-end of the molecules is towards oil droplet while the other end faces outside