Question

Identify the reaction/process in which the entropy increases.

• A. \(H(g)+H(g)\rightarrow H_2(g)\)
• B. \(H_2O(g)\rightarrow H_2O(s)\)
• C. \(H_2O(l)\rightarrow H_2O(g)\)
• D. \(A(g)+B(g)+C(s)\rightarrow 2D(s)\)

Hint:

Entropy increases when: \[ \text{Solid} \rightarrow \text{Liquid} \rightarrow \text{Gas} \] and when the number of gaseous particles increases.

Answer 1

The Correct Option is C

Step 1: Recall the concept of entropy.
Entropy is a measure of randomness or disorder in a system.
Greater molecular freedom and randomness correspond to higher entropy.
In general, entropy increases in the order
\[ \text{Solid} \lt \text{Liquid} \lt \text{Gas} \]

Step 2: Analyze option (1).
\[ H(g)+H(g)\rightarrow H_2(g) \] Two gaseous particles combine to form one gaseous molecule.
Number of gaseous particles decreases, so randomness decreases.
Hence, entropy decreases.

Step 3: Analyze option (2).
\[ H_2O(g)\rightarrow H_2O(s) \] Gas changes directly into solid.
Molecular freedom decreases drastically.
Hence, entropy decreases.

Step 4: Analyze option (3).
\[ H_2O(l)\rightarrow H_2O(g) \] Liquid changes into gas.
Gas molecules possess much greater randomness and freedom of motion.
Hence, entropy increases.

Step 5: Analyze option (4).
\[ A(g)+B(g)+C(s)\rightarrow 2D(s) \] Reactants contain gases, while products are solids.
Randomness decreases significantly.
Hence, entropy decreases.

Step 6: Final conclusion.
Therefore, entropy increases in the process
\[ \boxed{H_2O(l)\rightarrow H_2O(g)} \]