Generally the major component of soap bars is :

\(CH_3(CH_2)_{16}COO^-Na^+\)

The correct answer is option 3. \(CH_3(CH_2)_{16}COO^-Na^+\).

Soap is typically made through a process called saponification, which involves the reaction of a fatty acid with a strong base, such as sodium hydroxide (NaOH) or potassium hydroxide (KOH). The most common type of fatty acid used in soap making is stearic acid, which has the chemical formula \(CH_3(CH_2)_{16}COOH\).

During saponification, the carboxylic acid functional group (\(COOH\)) of the fatty acid reacts with the hydroxide ion (\(OH^-\)) from the base. This reaction results in the formation of the salt of the fatty acid, known as a fatty acid salt or soap, and glycerol (glycerin) as a byproduct. The general reaction can be represented as follows:

\[\text{Fatty Acid} + \text{Base} \rightarrow \text{Fatty Acid Salt (Soap)} + \text{Glycerol}\]

In the case of stearic acid reacting with sodium hydroxide, the resulting soap is sodium stearate (\(CH_3(CH_2)_{16}COO^-Na^+\)), which is represented in option (3). The sodium ion (\(Na^+\)) is derived from the sodium hydroxide, and the stearate ion (\(CH_3(CH_2)_{16}COO^-\)) is derived from the stearic acid.

Sodium stearate is an effective surfactant, meaning it has both hydrophilic (water-attracting) and hydrophobic (water-repelling) properties. This allows it to interact with both water and oils, enabling it to emulsify and remove dirt, grease, and oils from surfaces, making it a key ingredient in soap bars.

So, in summary, option (3) \(CH_3(CH_2)_{16}COO^-Na^+\) represents the major component of soap bars, which is sodium stearate, formed through the saponification of stearic acid with sodium hydroxide.