Sample interview questions: Discuss the principles of chemical equilibrium and the role of thermodynamics in predicting equilibrium conditions.
Sample answer:
Principles of Chemical Equilibrium:
Chemical Equilibrium is a dynamic state in which the concentrations of reactants and products remain constant over time, even though the reactions continue to occur in both directions. This balance is achieved when the forward and reverse reaction rates become equal. Several principles govern chemical equilibrium:
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Law of Mass Action: The rate of a chemical reaction is proportional to the product of the concentrations of the reactants, each raised to its stoichiometric coefficient. This law mathematically describes the relationship between the concentrations of reactants and products at equilibrium.
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Equilibrium Constant (Keq): The equilibrium constant (Keq) is a numerical value that represents the ratio of the concentrations of the products and reactants at equilibrium. It is a constant at a given temperature and does not depend on the initial concentrations of the reactants.
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Le Chatelier’s Principle: If a change in conditions (temperature, pressure, or concentration) is applied to a system in equilibrium, the system will shift in a direction that counteracts the change and re-establishes equilibrium.
Role of Thermodynamics in Predicting Equilibrium Conditions:
Thermodynamics plays a crucial role in predicting equilibrium conditions by providing insights into the energy changes associated with chemical reactions and the spontaneity of the process:
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Gibbs Free Energy: The change in Gibbs free energy (∆G) is a thermodynamic function that measures the spontaneity of a reaction. At equilibrium, ∆G = 0, indicating that the forward and reverse reactions occur at the same rate.
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Spontaneity and Equilibrium: A reaction is spontaneous if ∆G is negative. In this case, the reaction proceeds toward completion, favoring the formation of products. If ∆G is positive, the reaction is non-spontaneous, and the reactants are favored. At equilibrium, ∆G is zero, and the reaction is neither spontaneous nor non-spontaneous.
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Temperature Dependence: The equilibrium constant (Keq) is temperature-dependent. For exothermic reactions (∆H < 0), increasing the temperature shifts the equ… Read full answer