Thermodynamics Terms

Step 1: Analyzing the statements.
- (i) Bases would be soapy when touched. This is true for bases like sodium hydroxide that feel slippery and soapy when touched.
- (ii) Malic acid is present in apples. This is correct. Malic acid is the predominant acid found in apples.
- (iii) Stearic acid is present in fats. This is true. Stearic acid is a common fatty acid found in animal fats.
- (iv) Toothpaste is acidic in nature. This is incorrect. Toothpaste is typically alkaline in nature.


Step 2: Conclusion.
Based on the above analysis, the correct statements are (i), (ii), and (iii).

Final Answer: .

Step 1: Understanding the reactivity.
Potassium (K) is a highly reactive element, particularly with water. It belongs to the alkali metals group, known for their high reactivity.

Step 2: Why other options are not highly reactive.
- (B) Ag (Argentum) is silver, which is less reactive compared to potassium.
- (C) Al (Aluminium) is reactive, but not as reactive as potassium.
- (D) Au (Aurum) is gold, known for its inert nature and low reactivity.

Final Answer: K (Potassium).