The correct answer is B. Soap is a mixture of sodium or potassium salts of monocarboxylic acids.
Monocarboxylic acids are organic compounds that have one carboxyl group (-COOH) attached to a hydrocarbon chain. The most common monocarboxylic acid is acetic acid, which is found in vinegar. Other examples of monocarboxylic acids include formic acid, propionic acid, and butyric acid.
Soap is made by reacting a fat or oil with an alkali, such as sodium hydroxide or potassium hydroxide. This reaction is called saponification. The result of saponification is a mixture of sodium or potassium salts of the fatty acids in the fat or oil. These salts are what give soap its cleansing properties.
When soap is dissolved in water, the sodium or potassium ions are attracted to the water molecules, while the fatty acid chains are attracted to each other. This causes the soap molecules to form micelles. Micelles are tiny spheres with the fatty acid chains on the inside and the water-loving ions on the outside.
The fatty acid chains are attracted to dirt and oil, because they are both nonpolar. When soap is applied to skin, the micelles surround the dirt and oil and lift them away from the skin. The water-loving ions on the outside of the micelles then help to rinse the dirt and oil away.
Soap is an effective cleanser because it is able to remove both water-soluble and oil-soluble substances. It is also gentle on skin, because it does not contain harsh chemicals.