Question

In which of the following processes entropy increases?
A. A liquid evaporates to vapour.
B. Temperature of a crystalline solid lowered from 130 K to 0 K.
C. 2NaHCO₃(s) → Na₂CO₃(s)+CO₂(g)+H₂O(g)
D. Cl₂(g) → 2Cl(g)
Choose the correct answer from the options given below:

• A. A and C
• B. A, B and D
• C. A, C and D
• D. C and D

Answer 1

The Correct Option is C

To determine in which processes entropy increases, we need to understand what entropy means: it is a measure of disorder or randomness in a system. Entropy generally increases when the number of possible states or configurations of a system increases. Let's analyze each process:

1. A. A liquid evaporates to vapour.
   During evaporation, a liquid transforms into a gas. Gases have more disorder than liquids since the molecules in a gas move more freely and occupy a greater volume. Thus, entropy increases.
2. B. Temperature of a crystalline solid lowered from 130 K to 0 K.
   Lowering the temperature of a solid typically reduces its entropy as the molecular motion decreases, leading to a more ordered system.
3. C. \(2\text{NaHCO}_3(s) \rightarrow \text{Na}_2\text{CO}_3(s)+\text{CO}_2(g)+\text{H}_2\text{O}(g)\)
   This is a chemical reaction where solid sodium bicarbonate decomposes to form solid sodium carbonate, carbon dioxide gas, and water vapor. The formation of gases from a solid increases the entropy significantly since gases have a higher level of disorder.
4. D. \(\text{Cl}_2(g) \rightarrow 2\text{Cl}(g)\)
   The dissociation of chlorine gas into chlorine atoms increases entropy. Though both are in the gaseous state, forming more particles (from one mole of \(\text{Cl}_2\) to two moles of \(\text{Cl}\)) leads to greater disorder.

Therefore, the correct answer is: A, C and D