Which processes involve increase in entropy?

Options

A. N2(g) + 3Cl2(g) => 2NCl3
B. H2O(g) => H2O(l)
C. 2H2O(l) => 2H2(g) + O2(g)
D. CO(g) + 2H2(g) =>CH3OH(l)`

Answer

To determine which processes involve an increase in entropy, we need to analyze each given reaction and consider the states of the reactants and products. Entropy, a measure of disorder or randomness in a system, tends to increase when a system transitions from a more ordered state to a less ordered state.

### Step-by-Step Solution:

1. **Identify the Reactions**:
- **Reaction 1**: N2 gas + 3Cl2 gas → 2NCl3
- **Reaction 2**: H2O gas → H2O liquid
- **Reaction 3**: 2H2O liquid → 2H2 gas + O2 gas
- **Reaction 4**: CO gas + 2H2 gas → CH3OH liquid

2. **Analyze Each Reaction**:
- **Reaction 1**:
- Reactants: 1 mole of N2 (gas) + 3 moles of Cl2 (gas) = 4 moles of gas
- Products: 2 moles of NCl3 (assumed to be gas)
- Change in moles of gas: 4 moles (reactants) → 2 moles (products)
- **Entropy Change**: Decrease in entropy (more moles of gas to fewer moles of gas).

- **Reaction 2**:
- Reactants: H2O (gas)
- Products: H2O (liquid)
- **Entropy Change**: Decrease in entropy (gas to liquid, more ordered).

- **Reaction 3**:
- Reactants: 2 moles of H2O (liquid)
- Products: 2 moles of H2 (gas) + 1 mole of O2 (gas) = 3 moles of gas
- Change in moles of gas: 2 moles (reactants) → 3 moles (products)
- **Entropy Change**: Increase in entropy (liquid to gas, more disorder).

- **Reaction 4**:
- Reactants: CO (gas) + 2H2 (gas) = 3 moles of gas
- Products: CH3OH (liquid)
- **Entropy Change**: Decrease in entropy (gas to liquid, more ordered).

3. **Conclusion**:
- The only reaction that involves an increase in entropy is **Reaction 3**: 2H2O (liquid) → 2H2 (gas) + O2 (gas). This is because the transition from liquid to gas results in a greater number of moles of gas, indicating increased disorder.

### Final Answer:
The process that involves an increase in entropy is **2H2O (liquid) → 2H2 (gas) + O2 (gas)**.

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