For a reaction `N_2+3H_2 hArr 2NH_3` , the value of `K_c` would depend upon

Options

A. initial concentration of the reactants
B. Pressure
C. temperature
D. all of the above

Answer

To determine what the value of \( K_c \) depends on for the reaction \( N_2 + 3H_2 \rightleftharpoons 2NH_3 \), we can follow these steps:

### Step 1: Understand the Reaction
The given reaction is:
\[ N_2 + 3H_2 \rightleftharpoons 2NH_3 \]
This is a chemical equilibrium reaction where nitrogen gas and hydrogen gas react to form ammonia.

### Step 2: Define \( K_c \)
The equilibrium constant \( K_c \) for this reaction is defined as:
\[ K_c = \frac{[NH_3]^2}{[N_2][H_2]^3} \]
where \([NH_3]\), \([N_2]\), and \([H_2]\) are the molar concentrations of ammonia, nitrogen, and hydrogen, respectively, at equilibrium.

### Step 3: Identify Factors Affecting \( K_c \)
The value of \( K_c \) is influenced by various factors. However, it is crucial to note that:

- **Temperature**: The primary factor that affects \( K_c \) is temperature. Changes in temperature can shift the equilibrium position and thus change the value of \( K_c \).
- **Concentration of Reactants and Products**: While the initial concentrations of reactants and products can affect the position of equilibrium, they do not change the value of \( K_c \) itself once equilibrium is established.
- **Pressure**: For reactions involving gases, changes in pressure can affect the position of equilibrium but do not change the value of \( K_c \) unless temperature changes.

### Step 4: Conclusion
From the above analysis, we conclude that the value of \( K_c \) for the reaction \( N_2 + 3H_2 \rightleftharpoons 2NH_3 \) depends solely on the temperature. Therefore, the correct answer is:

**Answer: Temperature (Option C)**

---