N2O4(g)→ 2NO2(g) In the endothermic reaction above, more products formed will be favored by

Analysis of the Question

This question tests your understanding of Le Chatelier’s Principle, which states that if a dynamic equilibrium is disturbed by changing the conditions (such as temperature, pressure, or concentration), the position of equilibrium shifts to counteract the change.

Concept Explanation

To determine how pressure affects an equilibrium reaction, we look at the number of moles of gas on both sides of the equation:

• Reactant side: $N_2O_4(g)$ = 1 mole of gas.
• Product side: $2NO_2(g)$ = 2 moles of gas.

Le Chatelier’s Principle regarding pressure:

• Increasing pressure shifts the equilibrium toward the side with fewer moles of gas to reduce the pressure.
• Decreasing pressure shifts the equilibrium toward the side with more moles of gas to increase the pressure.

Step-by-Step Solution

1. Identify the goal: We want to favor the formation of more products ($2NO_2$).
2. Compare moles: The product side has 2 moles, while the reactant side has only 1 mole.
3. Apply the rule: To favor the side with more moles (the product side), we must decrease the pressure of the system.
4. Evaluate the options: • Increasing pressure (Option B) would favor the reactant side (1 mole). • Decreasing volume (Option D) is equivalent to increasing pressure, so it would also favor the reactant side. • Decreasing pressure (Option C) allows the system to shift toward the side with more moles to fill the space, thus favoring the production of $NO_2$.

Conclusion

By decreasing the pressure, the system shifts to the right (the side with more gas molecules) to restore equilibrium, thereby producing more $NO_2$.

Exam Tip

Think of pressure like a crowd in a room: if you increase the pressure (squeeze the room), the molecules will try to "clump together" into the side with fewer moles to save space. If you decrease the pressure (expand the room), the molecules will "spread out" into the side with more moles to fill the extra space!