Which of the following statements are correct about equilibrium constant for a gaseous phase reaction.

Options

A. Equilibrium constant cxpressed in terms of partial pressures has the unit of `("concentration")^(Delta n)`
B. Equilibrium constant expressed in terms of concentrations has the unit of `("concentration")^(Delta n)`
C. quilibrium constant expressed in terms of relative activity (i.e. the activity of substance relative to its activity in standard state) has no unit.
D. Equilibrium constant is written simply as` k^(@)` in terms of relative activity = `k_(p) xx p^(@) ` where `p^(@)` = 100 k pa in standard state for gases

Answer

To determine which statements are correct about the equilibrium constant for a gaseous phase reaction, we can analyze each statement step by step.

### Step-by-Step Solution:

1. **Understanding the Equilibrium Constant (K)**:
The equilibrium constant (K) is a numerical value that expresses the ratio of the concentrations or partial pressures of products to reactants at equilibrium. It can be expressed in terms of concentration (Kc) or partial pressure (Kp).

2. **Statement Analysis**:
- **Statement 1**: "Equilibrium constant expressed in terms of partial pressure has the unit of concentration to the power delta n."
- **Analysis**: This statement is incorrect. The equilibrium constant expressed in terms of partial pressure (Kp) has units of pressure raised to the power of the change in moles of gas (Δn), which is the difference between the moles of gaseous products and reactants. Therefore, it should be expressed in units of pressure (e.g., atm or bar), not concentration.

- **Statement 2**: "Equilibrium constant expressed in terms of concentrations has the unit of concentration to the power delta n."
- **Analysis**: This statement is correct. When the equilibrium constant is expressed in terms of concentrations (Kc), it is indeed measured in units of concentration (e.g., mol/L) raised to the power of Δn (the difference in moles of products and reactants).

- **Statement 3**: "Relative equilibrium constant expressed in terms of relative activity has no unit."
- **Analysis**: This statement is correct. Relative activity is a ratio of two quantities with the same units, thus it is dimensionless and has no unit.

- **Statement 4**: "Equilibrium constant is written simply as K0 in terms of relative activity Kp into P0, where P0 is equal to 100 kilo Pascal in standard state of gases."
- **Analysis**: This statement is correct. The relationship between Kp and K0 (relative activity) is indeed expressed as K0 = Kp × P0, where P0 is the standard pressure (100 kPa).

3. **Conclusion**:
Based on the analysis:
- Statement 1 is incorrect.
- Statements 2, 3, and 4 are correct.

### Final Answer:
The correct statements about the equilibrium constant for a gaseous phase reaction are:
- Statement 2
- Statement 3
- Statement 4