Question

Identify the correct statements
I) Enthalpy is an intensive property
II) For, H$_2$O(l) $\longrightarrow$ H$_2$O(g) process, $\Delta S$ increases
III) Entropy is a state function

• A. I, II, III
• B. I, II only
• C. I, III only
• D. II, III only

Hint:

Remember the distinction between intensive and extensive properties: intensive properties (like temperature, density) are independent of the amount of substance, while extensive properties (like mass, volume, enthalpy, internal energy, entropy) depend on the amount of substance. Also, recall that entropy generally increases with increasing disorder or randomness (e.g., solid $\to$ liquid $\to$ gas) and that state functions depend only on the initial and final states, not the path.

Answer 1

The Correct Option is D

Step 1: Evaluate Statement I - Enthalpy is an intensive property
An intensive property is a physical property of a system that does not depend on the system's size or the amount of material in the system (e.g., temperature, density, pressure). An extensive property is a physical property that depends on the amount of matter in a sample (e.g., mass, volume, energy, enthalpy). Enthalpy (H) is a measure of the total heat content of a system. Its value depends on the amount of substance present. For example, 1 mole of a substance has a certain enthalpy, but 2 moles of the same substance will have twice that enthalpy. Therefore, enthalpy is an extensive property, not an intensive property. So, Statement I is Incorrect. Step 2: Evaluate Statement II - For, H$_2$O(l) $\longrightarrow$ H$_2$O(g) process, $\Delta S$ increases
Entropy (S) is a measure of the disorder or randomness of a system. The process H$_2$O(l) $\longrightarrow$ H$_2$O(g) represents the phase transition from liquid water to gaseous water (vaporization). In the gaseous state, molecules are much more dispersed and have greater freedom of movement compared to the liquid state, where molecules are more closely packed and have less translational freedom. This increased disorder and randomness in the gaseous phase implies higher entropy. Therefore, for the transition from liquid to gas, the entropy of the system increases, meaning $\Delta S>0$. So, Statement II is Correct. Step 3: Evaluate Statement III - Entropy is a state function
A state function (or function of state) is a property whose value depends only on the current state of the system, not on the path taken to reach that state. Examples include temperature, pressure, volume, internal energy, enthalpy, and entropy. Entropy is a fundamental thermodynamic property. The change in entropy for a process depends only on the initial and final thermodynamic states of the system, irrespective of the specific path or process followed between these states. So, Statement III is Correct. Step 4: Identify the Correct Combination of Statements
Based on our analysis: \begin{itemize} \item Statement I is Incorrect. \item Statement II is Correct. \item Statement III is Correct. \end{itemize} Therefore, the correct statements are II and III. Step 5: Analyze the Options
\begin{itemize} \item Option (1): I, II, III. Incorrect because Statement I is false. \item Option (2): I, II only. Incorrect because Statement I is false. \item Option (3): I, III only. Incorrect because Statement I is false. \item Option (4): II, III only. Correct, as both Statement II and Statement III are true. \end{itemize}