Consider the chemical equation in equilibrium:
[tex]2 H_2(g)+O_2(g) \Leftrightarrow 2 H_2 O(g)[/tex]
What will happen if the pressure of the system is increased?
A. The reaction will not change.
B. The reaction will stop completely.
Answer (2)
The problem involves a chemical reaction in equilibrium and asks what happens when the pressure is increased.
Le Chatelier's principle is applied, stating that the system will shift to relieve the stress.
The side with fewer moles of gas is favored when pressure increases.
Since the product side has fewer moles of gas, the equilibrium shifts towards the products.
Explanation
Understanding the Problem We are given a chemical reaction in equilibrium: 2 H 2 ( g ) + O 2 ( g ) ⇔ 2 H 2 O ( g ) . We need to determine what happens when the pressure of the system is increased.
Applying Le Chatelier's Principle To solve this, we will use Le Chatelier's principle, which states that if a change of condition (like pressure, temperature, or concentration) is applied to a system in equilibrium, the system will shift in a direction that relieves the stress. In this case, the stress is an increase in pressure.
Counting Moles of Gas The reaction will shift to the side with fewer moles of gas. Let's count the moles of gas on each side of the equation.
Reactants Side On the reactants side, we have 2 moles of H 2 ( g ) and 1 mole of O 2 ( g ) , for a total of 3 moles of gas.
Products Side On the products side, we have 2 moles of H 2 O ( g ) .
Determining the Shift Since the product side has fewer moles of gas (2 moles) than the reactants side (3 moles), the equilibrium will shift to the right (towards the products) to relieve the stress of increased pressure.
Conclusion Therefore, increasing the pressure will cause the reaction to shift towards the products.
Examples
Le Chatelier's principle is not just a theoretical concept; it has practical applications in various industrial processes. For example, in the Haber-Bosch process for synthesizing ammonia ( N 2 + 3 H 2 ⇔ 2 N H 3 ), high pressure is used to shift the equilibrium towards the production of ammonia, as the product side has fewer moles of gas. This principle helps optimize reaction conditions to maximize yield and efficiency in chemical manufacturing.
Increasing the pressure on the given chemical equilibrium will cause the reaction to shift towards the products side, favoring the formation of H 2 O ( g ) because it has fewer moles of gas. Thus, the correct choice is A. The reaction will not change. (It will shift to the products.)
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