For which of the following processes is `DeltaS` negative?

Options

A. `H_(2) (g) to 2 H (g)`
B. `N_(2) (g, 1 a t m) to N_(2) (g, 5 a t m )`
C. `C (''diamond") to C ("graphite")`
D. `N_(2) (g ,2 7 3 K) to N_(2) (g , 3 0 0 K)`

Explanation

To determine which of the given processes has a negative change in entropy (ΔS), we need to analyze each option based on the concept of entropy, which is a measure of disorder or randomness in a system. A negative ΔS indicates that the disorder of the system is decreasing.

### Step-by-Step Solution:

1. **Understanding Entropy (ΔS)**:
- Entropy (ΔS) is a measure of the disorder or randomness of a system.
- A positive ΔS indicates an increase in disorder, while a negative ΔS indicates a decrease in disorder.

2. **Analyzing Option A**:
- The reaction is: H₂(g) → 2 H(g).
- In this reaction, one molecule of diatomic hydrogen gas (H₂) is converted into two atoms of hydrogen gas (H).
- Since the number of gas particles increases, the disorder of the system increases.
- **Conclusion**: ΔS is positive for this process.

3. **Analyzing Option B**:
- The reaction is: N₂(g) + N₂(g) → N₂(g) (at 1 atm) → N₂(g) (at 5 atm).
- Here, we have two molecules of nitrogen gas at 1 atm pressure converting to one molecule of nitrogen gas at a higher pressure (5 atm).
- Increasing pressure generally leads to a decrease in volume and hence a decrease in disorder.
- **Conclusion**: ΔS is negative for this process.

4. **Analyzing Option C**:
- The reaction is: Carbon (diamond) → Carbon (graphite).
- Diamond is a more ordered structure compared to graphite, which has a more disordered arrangement of carbon atoms.
- The conversion from diamond to graphite results in an increase in disorder.
- **Conclusion**: ΔS is positive for this process.

5. **Analyzing Option D**:
- The reaction is: N₂(g) at 273 K → N₂(g) at 300 K.
- Here, we have nitrogen gas at a lower temperature (273 K) being heated to a higher temperature (300 K).
- Increasing temperature typically increases the kinetic energy of the molecules, leading to greater disorder.
- **Conclusion**: ΔS is positive for this process.

### Final Conclusion:
After analyzing all the options, the only process that results in a negative change in entropy (ΔS < 0) is **Option B**.