Which of the following feels soapy on touching? 

Base 

The correct answer is option 2. Base.

When you touch a base, it may feel soapy or slippery. This is a characteristic property of bases. The slippery feeling is due to the saponification of skin oils by the base. Bases are substances that can accept protons (H⁺ ions) in aqueous solutions.

One common example of a base that exhibits this soapy feel is sodium hydroxide (NaOH), also known as caustic soda or lye. When sodium hydroxide comes into contact with the skin, it reacts with the fats and oils present in the skin through a process called saponification. This reaction produces soap (a type of salt) and glycerol.

The general saponification reaction can be represented as follows:

\[ \text{Base (NaOH)} + \text{Fat or Oil} \rightarrow \text{Soap} + \text{Glycerol} \]

The soap produced in this reaction is responsible for the slippery or soapy feel. This property is often used as a simple and qualitative way to identify whether a substance is basic. It is important to note that not all bases feel soapy, but those that are capable of saponifying fats and oils will exhibit this characteristic.