In chemical reactions, equilibrium is reached when the rates of the forward and reverse reactions are equal. The equilibrium constant, $K$, quantifies the ratio of products to reactants at equilibrium. When dealing with gases, we use $K_p$, which is expressed in terms of partial pressures. For reactions in solution, we use $K_c$, which is expressed in terms of molar concentrations. Understanding the relationship between $K_p$ and $K_c$ and how to calculate them is crucial for predicting the direction and extent of a reaction.
The relationship between $K_p$ and $K_c$ is given by the equation: $K_p = K_c(RT)^{\Delta n}$, where $R$ is the ideal gas constant, $T$ is the temperature in Kelvin, and $\Delta n$ is the change in the number of moles of gas between products and reactants.
Match each term with its correct definition:
| Term | Definition |
|---|---|
| 1. Equilibrium Constant ($K$) | A. The pressure exerted by a gas in a mixture. |
| 2. $K_p$ | B. The state where the rates of forward and reverse reactions are equal. |
| 3. $K_c$ | C. The ratio of product concentrations to reactant concentrations at equilibrium. |
| 4. Partial Pressure | D. The equilibrium constant expressed in terms of partial pressures. |
| 5. Equilibrium | E. The equilibrium constant expressed in terms of molar concentrations. |
Complete the following paragraph using the words provided: products, reactants, equilibrium, constant, concentrations.
At __________, the rate of the forward reaction equals the rate of the reverse reaction. The equilibrium __________ ($K$) expresses the ratio of __________ to __________ at equilibrium. $K_c$ uses molar __________, while $K_p$ uses partial pressures.
Explain how changing the temperature affects the equilibrium constant ($K$) for an exothermic reaction. Use Le Chatelier's principle in your explanation.
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