Question

Following are statements of a few processes taking place in nature.
I. Free expansion of a gas
II. The combustion of a mixture of petrol and air ignited by a spark
III. The leaking of gas from the kitchen cylinder
IV. The transfer of heat from one heated part of a liquid to the other colder part
Which amongst these processes are irreversible in nature?

• A. I and II
• B. III and IV
• C. II, III and IV
• D. I, II, III and IV

Hint:

A simple rule: If a process occurs spontaneously in nature, it is typically irreversible. Reversible processes are idealizations that involve infinitesimally slow changes and no dissipative forces (like friction or unrestrained expansion).

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks to identify which of the listed natural processes are irreversible. An irreversible process is one that cannot be undone without leaving some change in the surroundings. All spontaneous natural processes are irreversible.
Step 3: Detailed Explanation:
1. Free expansion of a gas: This is a spontaneous process where a gas expands into a vacuum. It cannot be reversed spontaneously without external work. Thus, it is irreversible.
2. The combustion of a mixture of petrol and air ignited by a spark: Combustion is a highly exothermic and spontaneous chemical reaction. It cannot be reversed spontaneously. Thus, it is irreversible.
3. The leaking of gas from the kitchen cylinder: Gas leaking from a high-pressure region to a low-pressure region (atmosphere) is a spontaneous and unrestrained expansion. It cannot be reversed to get the gas back into the cylinder without doing work. Thus, it is irreversible.
4. The transfer of heat from one heated part of a liquid to the other colder part: Heat always flows spontaneously from a hotter body to a colder body (second law of thermodynamics). It cannot spontaneously flow from cold to hot. Thus, it is irreversible.
All four processes are spontaneous natural phenomena and are therefore irreversible.
Step 4: Final Answer:
All processes (I, II, III, and IV) are irreversible in nature.