Consider the following chemical reaction in a small volume of solution. According to LeChatelier’s Principle, which perturbation will shift the reaction towards the left (towards reactants)? 2CrO42- + 2H+ ↔ Cr2O72- + H2O + Heat

Decreasing the temperature will shift the equilibrium leftwards towards reactants.

Explanation:

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In this case, since the reaction between chromate anions and hydrogen ions yields dichromate anions, water and heat, we can infer this is an exothermic reaction by which heat is released (remember in endothermic reactions heat is absorbed as a reactant), it means that considering the LeChatelier’s which states that increasing the temperature of an exothermic reaction shifts the equilibrium leftwards since heat is a product, otherwise (decreasing the temperature) the equilibrium will be shifted rightwards.

Therefore, decreasing the temperature is the perturbation that will shift the equilibrium leftwards towards the reactants.

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