Mark the correct statement

Options

A. For a chemical reaction to be feasible, `DeltaG` should be zero
B. Entropy is a measure of order in a system
C. For a chemical reaction to be feasible, `DeltaG` should be positive
D. The total energy of an isolated system is constant

Explanation

To solve the question, we need to analyze the statements regarding thermodynamics, particularly focusing on the Gibbs free energy (ΔG) and the concept of entropy (S). The goal is to identify the correct statement among the options provided.

### Step-by-Step Solution:

1. **Understanding Gibbs Free Energy (ΔG):**
- For a chemical reaction to be feasible (spontaneous), the change in Gibbs free energy (ΔG) must be less than 0 (ΔG < 0). This indicates that the reaction can occur without the input of additional energy.
- If ΔG = 0, the system is at equilibrium, meaning the forward and reverse reactions occur at the same rate, and there is no net change.
- If ΔG > 0, the reaction is non-spontaneous, meaning it requires energy input to proceed.

2. **Analyzing Entropy (S):**
- Entropy is a measure of the disorder or randomness in a system. A higher entropy value indicates a more disordered state.
- The statement that "entropy is a measure of order in the system" is incorrect because entropy actually measures disorder, not order.

3. **Evaluating the Statements:**
- **Statement 1:** "For a chemical reaction to be feasible, ΔG should be 0." - This is incorrect because ΔG should be less than 0 for feasibility.
- **Statement 2:** "Entropy is a measure of order in the system." - This is incorrect because entropy measures disorder.
- **Statement 3:** "For a chemical reaction to be feasible, ΔG should be positive." - This is incorrect because ΔG should be less than 0 for feasibility.
- **Statement 4:** "The total energy of an isolated system is constant." - This is correct. In an isolated system, no energy is exchanged with the surroundings, so the total energy remains constant.

4. **Conclusion:**
- The correct statement among the options is: "The total energy of an isolated system is constant."

### Final Answer:
The correct statement is: **"The total energy of an isolated system is constant."**