Problem 68 - Chemistry The Science in Context

Question

How will the changes listed affect the position of the following equilibrium? $$ 2 \mathrm{NO}_{2}(g) \rightleftharpoons \mathrm{NO}(g)+\mathrm{NO}_{3}(g) $$ a. The concentration of \(\mathrm{NO}\) is increased. b. The concentration of \(\mathrm{NO}_{2}\) is increased. c. The volume of the system is allowed to expand to 5 times its initial value.

Step-by-Step Solution

Answer

Answer: a. The equilibrium will shift to the left when the concentration of NO is increased. b. The equilibrium will shift to the right when the concentration of NO2 is increased. c. The equilibrium will shift to the left when the volume of the system is allowed to expand.

Step 1: Understand Le Chatelier's Principle

Le Chatelier's Principle states that when a system at equilibrium experiences changes, the equilibrium will shift to oppose those changes. In this case, we have a reaction of gases, and we'll consider the following parameters: concentration and volume. The equilibrium will try to neutralize the impact of these changes.

Step 2: Analyze the effect of increasing the concentration of NO

As per Le Chatelier's Principle, when the concentration of NO (a product) is increased, the equilibrium will try to counteract the change by shifting in the direction that will decrease the concentration of NO. So, the reaction will shift to the left (the direction of reactant formation).

Step 3: Analyze the effect of increasing the concentration of NO2

When the concentration of NO2 (a reactant) is increased, the equilibrium will try to counteract the change by shifting in a direction that will decrease the concentration of NO2. In this case, the reaction will shift to the right (the direction of product formation).

Step 4: Analyze the effect of increasing the volume of the system

When the volume is increased, the pressure in the system will decrease. To counteract this change, the equilibrium will shift in the direction that produces more molecules of gas, as this will tend to increase the pressure. Since the left side of the equilibrium equation has more molecules (2 NO2) than the right side (1 NO + 1 NO3), the reaction will shift to the left (the direction of reactant formation). To summarize: a. When the concentration of NO is increased, the equilibrium shifts to the left. b. When the concentration of NO2 is increased, the equilibrium shifts to the right. c. When the volume of the system is allowed to expand, the equilibrium shifts to the left.

Key Concepts

Chemical Equilibrium

Chemical equilibrium refers to the state in a chemical reaction where the rate of the forward reaction is equal to the rate of the backward reaction.
This balance results in the concentrations of the reactants and products remaining constant over time.
It is important to note that equilibrium does not mean that the concentrations are equal, but rather that their ratios remain constant. At this point, we say the reaction has reached a dynamic equilibrium. Although the reactions continue to occur, there is no net change in the concentration of substances.
Equilibrium is a critical concept because it reflects the state of balance in a chemical system, such as the gaseous reaction given - The reaction equation: - \( 2 \mathrm{NO}_{2}(g) \rightleftharpoons \mathrm{NO}(g)+\mathrm{NO}_{3}(g) \)- In this reaction, both NO and NO\(_2\) gases exist in equilibrium with one another. To understand how certain factors, like concentration and volume, affect the system, we apply Le Chatelier's Principle to predict the direction in which the equilibrium will shift.

Reaction Shifts

Reaction shifts occur when a system at equilibrium undergoes a change in conditions, prompting the equilibrium to move in a direction that helps counterbalance that change.
This behavior is described by Le Chatelier's Principle.
Depending on whether reactants or products are added or removed, the equilibrium shifts to restore balance.### Influences on Equilibrium- **Change in concentration:** If a product or reactant concentration is increased, the system shifts in the opposite direction to reduce the change. - Example: Increasing \( \mathrm{NO} \) causes the reaction to shift left, forming more \( \mathrm{NO}_{2} \).- **Change in volume or pressure:** Variations in volume or pressure will cause the equilibrium to move towards the side with more or fewer moles to minimize changes in pressure. - Example: Expanding the volume causes the pressure to drop, causing the reaction to shift left, where more gas moles exist.Understanding these shifts can provide insight into the behavior of gases in a reaction and how equilibrium can be manipulated or maintained.

Gas Concentration Changes

Gas concentration changes can significantly impact a reaction at equilibrium, especially in gaseous systems.
When concentration changes, the equilibrium tries to adjust to offset these changes, according to Le Chatelier's Principle. ### Effects of Concentration Changes- **Increasing product concentration:** More of a product like \( \mathrm{NO} \) drives the reaction backward or to the left, as it seeks to use up the excess product by forming reactants.- **Increasing reactant concentration:** Adding \( \mathrm{NO}_{2} \) results in a shift to the right, producing more products to lower the concentration of the excess reactants.These adjustments show how the system naturally tries to maintain its state of balance.
This behavior is an essential aspect of understanding reaction dynamics, and how changing gas concentrations can be strategically used in chemical processes to yield more desired products or maintain stability.