Points to Remember:
- Equilibrium constant (Kc) expression
- Units of the equilibrium constant
- Relationship between Kc and the stoichiometric coefficients
Introduction:
Chemical equilibrium is a state where the rates of the forward and reverse reactions are equal, resulting in no net change in the concentrations of reactants and products. The equilibrium constant (Kc) quantifies this equilibrium. It’s a ratio of the concentrations of products to reactants, each raised to the power of its stoichiometric coefficient in the balanced chemical equation. The value of Kc indicates the extent to which a reaction proceeds to completion at a given temperature. A large Kc indicates that the equilibrium lies far to the right (favoring products), while a small Kc indicates that the equilibrium lies far to the left (favoring reactants).
Body:
1. Writing the Equilibrium Constant Expression:
The given reaction is:
4 NHâ(g) + 5Oâ(g) â 4NO(g) + 6HâO(g)
The equilibrium constant expression (Kc) is written as the ratio of the concentrations of products to the concentrations of reactants, each raised to the power of its stoichiometric coefficient:
Kc = ([NO]â´[HâO]â¶) / ([NHâ]â´[Oâ]âµ)
2. Determining the Units of the Equilibrium Constant:
The units of Kc depend on the stoichiometry of the reaction. To find the units, we examine the expression:
Kc = ([mol/L]â´[mol/L]â¶) / ([mol/L]â´[mol/L]âµ)
Simplifying, we get:
Kc = [mol/L]¹ = mol/L or M (Molarity)
Conclusion:
In summary, the equilibrium constant (Kc) for the reaction 4 NHâ(g) + 5Oâ(g) â 4NO(g) + 6HâO(g) is:
Kc = ([NO]â´[HâO]â¶) / ([NHâ]â´[Oâ]âµ)
The units of Kc for this specific reaction are mol/L or M (Molarity). Understanding the equilibrium constant and its units is crucial in predicting the direction and extent of a chemical reaction under various conditions. Further analysis could involve investigating the effect of temperature and pressure on the equilibrium position and the value of Kc. This knowledge is fundamental to various industrial processes, such as the Haber-Bosch process for ammonia synthesis, which relies on manipulating equilibrium conditions to maximize product yield. A thorough understanding of chemical equilibrium contributes to efficient and sustainable chemical production.
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