If the reaction A(g) ⇌ B(g) has an equilibrium constant K much less than 1, and heat is added, how will the concentrations change if the reaction is exothermic?
Understand the Problem
The question describes a gaseous reaction at equilibrium with an equilibrium constant K << 1. It asks how the concentrations of reactants ([A]) and products ([B]) will change when heat is added to the system, given that the reaction is exothermic. The key here is understanding how exothermic reactions and the magnitude of K influence the equilibrium shift upon heating.
Answer
Adding heat increases [A] and decreases [B].
For the exothermic reaction A(g) ⇌ B(g) with K << 1, adding heat will shift the equilibrium towards the reactants (A), thus increasing the concentration of A and decreasing the concentration of B.
Answer for screen readers
For the exothermic reaction A(g) ⇌ B(g) with K << 1, adding heat will shift the equilibrium towards the reactants (A), thus increasing the concentration of A and decreasing the concentration of B.
More Information
Le Chatelier's principle states that if a change of condition is applied to a system in equilibrium, the system will shift in a direction that relieves the stress. In an exothermic reaction, heat is considered a product. Increasing the temperature drives the equilibrium towards the reactants.
Tips
A common mistake is to assume all reactions shift in the same direction when heat is added. Remember to consider whether the reaction is exothermic or endothermic.
Sources
- The Effect of Changing Conditions - Chemistry LibreTexts - chem.libretexts.org
- Exothermic vs. Endothermic and K - Chemistry LibreTexts - chem.libretexts.org
- Le Chȃtelier's principle: Changing temperature - Khan Academy - khanacademy.org
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