Question:
Which of the following reactions exhibits decrease in entropy?
Which of the following reactions exhibits decrease in entropy?
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Count gas moles: Fewer gas moles in products $\rightarrow$ Decrease in Entropy.
Updated On: May 14, 2026
- $2\text{H}_2\text{O}_{2(l)} \longrightarrow 2\text{H}_2\text{O}_{(l)} + \text{O}_{2(g)}$
- $\text{H}_{2(g)} \longrightarrow 2\text{H}_{(g)}$
- $\text{CaCO}_{3(s)} \xrightarrow{\Delta} \text{CaO}_{(s)} + \text{CO}_{2(g)}$
- $2\text{H}_{2(g)} + \text{O}_{2(g)} \longrightarrow 2\text{H}_2\text{O}_{(l)}$
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Verified By Collegedunia
The Correct Option is D
Solution and Explanation
Step 1: Concept Entropy ($S$) decreases when randomness decreases, typically when gas moles are consumed or gas converts to liquid/solid.
Step 2: Meaning A positive $\Delta S$ means increased randomness; a negative $\Delta S$ means decreased randomness.
Step 3: Analysis (A), (B), and (C) produce more gas moles than they consume, increasing entropy. In (D), 3 moles of gas combine to form 2 moles of liquid, leading to a significant loss of randomness.
Step 4: Conclusion Reaction (D) shows a decrease in entropy ($\Delta S < 0$). Final Answer: (D)
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