Question

In which of the following entropy decreases?

• A. Preparing aqueous solution of common salt.
• B. Change of water into ice.
• C. Dry ice placed in an open vessel.
• D. Melting of ice.

Answer 1

The correct option is D Melting of ice.

Entropy can understood as the measure of randomness or disorder in a system. The more randomness in a system means the entropy of the system is higher.

Let's understand the options in an easy way:

(A) Preparing aqueous solution of common salt.

- Here, solid NaCl is mixed with water to form an aqueous solution. So randomness is increasing. hence entropy is increasing.

(B) Change of water into ice- matter in solid state are more organized. Hence randomness is decreasing here: Entropy decreases.

(C) Dry ice placed in an open vessel: Solid carbon dioxide will turn into gaseous carbon dioxide. Randomness will increase: Entropy increases.

(D) Melting of ice: Solid to liquid transformation. So randomness increases: entropy increases.