Pressure changes can have a big impact on gas reactions. We can understand this using a rule called Le Chatelier's Principle. This principle tells us that if a balanced system is disturbed, it will try to fix itself by shifting in a way that reduces the disturbance and brings back balance.

To see how pressure affects gas reactions, we focus on how many gas particles are on each side of the reaction. Changes in pressure mostly influence gas reactions because gases can be squeezed together easily. Let’s look at some important points:

How Pressure Affects Equilibrium

1. When Pressure Increases: If we increase the pressure in a gas reaction, the balance will shift toward the side with fewer gas particles. This happens because having fewer gas particles lowers the overall pressure, which helps ease the pressure stress.

   Example: Take this reaction: $N_2(g) + 3 H_2(g) \rightleftharpoons 2 NH_3(g)$
   On the left side, there are 4 gas particles (1 nitrogen and 3 hydrogen), while the right side has 2 gas particles (2 ammonia). If we increase the pressure, the balance shifts to the right, producing more ammonia. This reduces the number of gas particles and helps lower the pressure.

2. When Pressure Decreases: On the other hand, if we lower the pressure, the balance shifts toward the side with more gas particles. This shift helps increase the overall pressure by creating more gas.

   Example: Using the same reaction: $N_2(g) + 3 H_2(g) \rightleftharpoons 2 NH_3(g)$
   If the pressure decreases, the balance shifts to the left, encouraging the production of nitrogen and hydrogen gases. This increases the number of gas particles and helps bring the pressure back up.

Important Takeaways

• Increasing Pressure → Shift to Fewer Particles: The balance shifts toward the side with fewer gas particles.
• Decreasing Pressure → Shift to More Particles: The balance shifts toward the side with more gas particles.

These examples show us how pressure plays a key role in gas reactions. Whether you're increasing or decreasing pressure, the way the system reacts is a fascinating part of understanding chemical balances!