According to the second law of thermodynamics, a process (reaction) is spontaneous, if during the process

Options

A. `triangleS_("universe") gt 0`
B. `triangleS_("universe") = 0`
C. `triangleH_("system") gt 0`
D. `triangleS_("universe") = triangleS_("system")`

Answer

To determine whether a process (reaction) is spontaneous according to the second law of thermodynamics, we can follow these steps:

### Step 1: Understand the Second Law of Thermodynamics
The second law of thermodynamics states that the total entropy of an isolated system can never decrease over time. It can either increase or remain constant in the case of reversible processes.

### Step 2: Define Entropy
Entropy (S) is a measure of the randomness or disorder of a system. The change in entropy of the universe (ΔS_universe) is the sum of the change in entropy of the system (ΔS_system) and the change in entropy of the surroundings (ΔS_surroundings).

### Step 3: Identify Conditions for Spontaneity
A process is considered spontaneous if the change in entropy of the universe is greater than zero:
\[ \Delta S_{universe} > 0 \]
This means that the total entropy of the system and the surroundings must increase.

### Step 4: Analyze the Options
- **Option 1**: The process is spontaneous if the change in entropy of the universe is greater than zero (ΔS_universe > 0). This is correct.
- **Option 2**: The process remains constant for reversible processes. This is not correct as it does not indicate spontaneity.
- **Option 3**: The use of enthalpy (ΔH) is not relevant in the context of the second law of thermodynamics for determining spontaneity.

### Conclusion
Thus, according to the second law of thermodynamics, a process is spontaneous if during the process:
\[ \Delta S_{universe} > 0 \]
This confirms that **Option 1** is the correct answer.

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