equilibrium 2

• What is the formula for calculating Kc?

  Kc is equal to the concentration of the products divided by the concentration of the reactants.

  
• How are the concentration terms treated in the Kc expression?

  The concentration terms are raised to a power equal to the number of moles of that substance.
• What affects the units of Kc?

  • The units of Kc vary depending on the chemical reaction.
  • Units can be calculated by substituting concentration units into the Kc expression.
  • Some units will cancel, giving the overall units of Kc for that reaction.

  
• What types of reactions can Kc be calculated for?

  Kc can be calculated for both homogeneous and heterogeneous reactions.

  
• What distinguishes homogeneous reactions from heterogeneous reactions?

  Homogeneous reactions have reactants and products in the same phase, while heterogeneous reactions have some in different phases.

  
• How is Kc calculated for homogeneous reactions?

  Kc is calculated using the concentration of products and reactants as shown previously.

  
• What is the difference in calculating Kc for heterogeneous reactions?

  In heterogeneous reactions, any terms representing a solid are not included in the calculation.

  
• What is Kp used for?

  Kp is the equilibrium constant used for gaseous equilibria.
• When is a system considered homogeneous in terms of Kp?

  A system is homogeneous if all reactants and products are in the gaseous state.
• What is the definition of partial pressure in a gaseous system?

  The partial pressure of a substance is found using the molar fraction of that substance and the total pressure of the system.
• How is the partial pressure of a gas represented?

  The partial pressure of gas A is represented as (P​A​).
• In what units are partial pressures commonly measured?

  Partial pressures are commonly measured in Pascals but can also be measured in atmospheres.
• How do you calculate the partial pressure of H​2​ given the total moles in the system?

  The partial pressure of H​2​ is calculated as (P​H​2​) = molar fraction of H​2​ x total pressure.

  
• What is the relationship between Kp and partial pressures?

  Kp is equal to the product of the partial pressures of products over the product of the partial pressures of reactants.
• How are the units of Kp determined?

  The units of Kp vary depending on the chemical reaction and can be calculated by substituting the partial pressure units into the Kp expression.
• What is the difference in calculating Kp for heterogeneous reactions?

  • In heterogeneous reactions, any terms representing a solid are not included in the calculation.
  • This is similar to the calculation of Kc for heterogeneous reactions.

  
• How do Kc and Kp differ in terms of their dependence on concentration and pressure changes?

  The values of Kc and Kp are not affected by concentration or pressure changes or by the use of a catalyst.
• What effect does temperature have on Kc and Kp?

  Temperature affects the position of the equilibrium, resulting in different concentrations of reactants and products, thus changing the equilibrium constant.

  
• How does an increase in temperature affect an exothermic reaction's equilibrium constant?

  An increase in temperature will decrease the equilibrium constant (Kc or Kp) for an exothermic reaction.

  
• How does an increase in temperature affect an endothermic reaction's equilibrium constant?

  An increase in temperature will increase the equilibrium constant (Kc or Kp) for an endothermic reaction.

  
• What are the effects of decreasing temperature on Kc and Kp?

  • Decreasing temperature will affect the position of the equilibrium.
  • For exothermic reactions, it will increase the equilibrium constant (Kc or Kp).
  • For endothermic reactions, it will decrease the equilibrium constant (Kc or Kp).

  
• What is the formula for mole fraction of a gas?

  Mole fraction of gas = Number of moles of particular gas / Total number of moles of all gases in the mixture
• What is partial pressure?

  Partial pressure is the pressure exerted by a particular gas in a mixture in a closed system
• How is partial pressure related to mole fraction and total pressure?

  Partial pressure = Mole fraction x Total pressure
• What is total pressure in a gas mixture?

  Total pressure is the sum of all partial pressures
• Given a mixture of gases, how do you calculate the total number of moles if you have 0.005 moles of N₂, 0.010 moles of O₂, and 0.020 moles of Ar?

  • Total number of moles = 0.005 + 0.010 + 0.020
  • Total number of moles = 0.035 mol
• How do you calculate the mole fractions of nitrogen, oxygen, and argon in a gas mixture with a total of 0.035 moles?

  • Mole fraction of Nitrogen = \( \frac{0.005}{0.035} = \frac{1}{7} \)
  • Mole fraction of Oxygen = \( \frac{0.010}{0.035} = \frac{2}{7} \)
  • Mole fraction of Argon = \( 1 - \left(\frac{1}{7} + \frac{2}{7}\right) = \frac{4}{7} \)
• How do you calculate the partial pressures of nitrogen, oxygen, and argon in a mixture with a total pressure of 140 bars?

  • Partial pressure of Nitrogen = \( \left(\frac{1}{7}\right) \times 140 = 20 \text{ bar} \)
  • Partial pressure of Oxygen = \( \left(\frac{2}{7}\right) \times 140 = 40 \text{ bar} \)
  • Partial pressure of Argon = \( 140 - (20 + 40) = 80 \text{ bar} \)
• What is the relationship between the reaction quotient and the equilibrium constant (Kc, Kp)?

  Only at equilibrium is the reaction quotient the same as the equilibrium constant
• What does the reaction quotient represent in a chemical system?

  The reaction quotient represents the ratio of the concentrations of products to reactants at any point in the reaction
• When can the values in the reaction quotient be considered equal to the equilibrium constant?

  When the system is at equilibrium