Question

Observe the following reactions:
I. \( \text{CaCO}_3(s) \rightarrow \text{CaO}(s) + \text{CO}_2(g) \)
II. \( \text{Cl}_2(g) \rightarrow 2 \text{Cl}(g) \)
III. \( \text{H}_2\text{O}(l) \rightarrow \text{H}_2O(s) \)
Identify the reactions in which entropy increases.

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

Hint:

In chemical reactions, an increase in the number of gas molecules or particles leads to an increase in entropy.

Answer 1

The Correct Option is B

In general, entropy increases when the system's disorder increases. Let's analyze the reactions:
In reaction I, \( \text{CaCO}_3 \) breaks down into \( \text{CaO} \) and \( \text{CO}_2 \), increasing the number of moles of gases, which leads to an increase in entropy.
In reaction II, the chlorine molecule dissociates into two chlorine atoms, which increases the disorder and entropy.
In reaction III, the transition from liquid to solid reduces the disorder, and thus entropy decreases.