Mass action rato or reaction quotient Q for a reaction can be calculate using the law of masss action
`A(g)+B(g) hArr C(g)+D(g)`
`Q=([C][D])/([A][B])`
The value of Q decides whether the reaction is at equilibrium or not.
At equilibrium, `Q=K`
For an equilibrium process, `Q ne K`
when `Q gt K`, reaction will favour backward direction and when `Q lt K`, it will favour forward direction.
Answer the following questions:
In a reaction mixture containing `H_(2), N_(2)` and `NH_(3)` at partial pressure of `2` atm, `1` atm and `3` atm respectively, the value of `K_(p)` at `700 K` is `4.00xx10^(-5) atm^(-2)`. In which direction the net reaction will go?
`N_(2)(g)+3H_(2)(g) hArr 2NH_(3)(g)`

Options

A. Forward
B. Backward
C. No reaction
D. Cannot be predicted

Explanation

To determine the direction of the net reaction for the given equilibrium involving nitrogen gas (N₂), hydrogen gas (H₂), and ammonia (NH₃), we will follow these steps:

### Step 1: Write the balanced chemical equation
The balanced chemical equation for the reaction is:
\[ N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g) \]

### Step 2: Write the expression for the reaction quotient (Q)
The reaction quotient \( Q \) can be calculated using the partial pressures of the gases involved in the reaction:
\[ Q = \frac{(P_{NH_3})^2}{(P_{N_2})(P_{H_2})^3} \]

### Step 3: Substitute the given partial pressures into the expression for Q
From the problem, we have:
- \( P_{NH_3} = 3 \, \text{atm} \)
- \( P_{N_2} = 2 \, \text{atm} \)
- \( P_{H_2} = 1 \, \text{atm} \)

Substituting these values into the expression for \( Q \):
\[ Q = \frac{(3)^2}{(2)(1)^3} = \frac{9}{2} = 4.5 \]

### Step 4: Compare Q with Kp
The equilibrium constant \( K_p \) at 700 K is given as:
\[ K_p = 4.00 \times 10^{-5} \, \text{atm}^{-2} \]

Now, we compare \( Q \) and \( K_p \):
- \( Q = 4.5 \)
- \( K_p = 4.00 \times 10^{-5} \)

### Step 5: Determine the direction of the reaction
Since \( Q > K_p \):
- According to the principles of chemical equilibrium, when \( Q > K \), the reaction will favor the backward direction (the formation of reactants).

### Conclusion
The net reaction will proceed in the backward direction.

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