Given the following reaction, what will cause no impact on the equilibrium if the forward reaction is endothermic?
[tex]2 PbS(s)+3 O_2(g)+C(s) \rightleftharpoons 2 Pb(s)+CO_2(g)+2 SO_2(g)[/tex]
A. decreasing pressure
B. adding [tex]SO _2[/tex]
C. adding [tex]O _2[/tex]
D. putting the reaction in an ice bath
Answer (2)
The reaction involves an equilibrium between solid and gaseous species.
Decreasing pressure will not impact the equilibrium because the number of moles of gas is the same on both sides of the reaction.
Adding S O 2 or O 2 will shift the equilibrium.
Cooling the reaction will shift the equilibrium towards the reactants.
Therefore, the answer is decreasing pressure.
Explanation
Understanding the Reaction and Equilibrium We are given the reaction: 2 P b S ( s ) + 3 O 2 ( g ) + C ( s ) ⇌ 2 P b ( s ) + C O 2 ( g ) + 2 S O 2 ( g )
The forward reaction is endothermic, meaning it absorbs heat. We need to determine which of the given changes will have no impact on the equilibrium.
Analyzing Each Option Let's analyze each option:
Decreasing pressure: According to Le Chatelier's principle, decreasing the pressure will shift the equilibrium towards the side with more moles of gas. In this reaction, the reactant side has 3 moles of O 2 ( g ) , while the product side has 1 mole of C O 2 ( g ) and 2 moles of S O 2 ( g ) , totaling 3 moles of gas. Since both sides have the same number of moles of gas, changing the pressure will have no effect on the equilibrium.
Adding S O 2 : Adding a product will shift the equilibrium towards the reactant side to relieve the stress.
Adding O 2 : Adding a reactant will shift the equilibrium towards the product side to relieve the stress.
Putting the reaction in an ice bath: Since the forward reaction is endothermic, it absorbs heat. Cooling the reaction (putting it in an ice bath) will shift the equilibrium towards the reactant side, as it favors the exothermic (reverse) reaction.
Determining the Answer Based on the analysis above, decreasing the pressure will cause no impact on the equilibrium because the number of moles of gas is the same on both sides of the reaction.
Examples
Consider an industrial process where lead is produced from lead sulfide. Understanding how different factors affect the equilibrium of the reaction is crucial for optimizing the production process. For instance, knowing that changing the pressure won't affect the equilibrium allows engineers to focus on other factors like temperature or reactant concentrations to maximize lead yield. This ensures efficient use of resources and cost-effective production.
The correct answer is A. decreasing pressure, as it does not affect the equilibrium due to the equal number of gas moles on both sides of the reaction. Other changes, such as adding products or lowering the temperature, will shift the equilibrium. Understanding Le Chatelier's principle helps to predict these shifts in equilibrium.
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