Equilibrium Constant Kp for Homogeneous Systems

• reversible reactions take place in the gas phase
• partial pressure: the pressure that the gas would exert if it occupied the container on its own
• in a mixture of gases, each gas contributes to the total pressure - this contribution is partial pressure
• partial pressure equation?


  mole fraction of A x total pressure
• mole fraction equation?


  number of moles of gas A in mixture / total number of moles of gas in the mixture
• what happens when a reaction is exothermic?

  the reaction is going left to right, increasing the temperature forces the equilibrium to the left, so the reaction absorbs heat. increasing temperature, decreases Kp and decreases yield of products at equilibrium
• what happens when pressure increases?

  forces equilibrium to reduce the total pressure, to the side with fewer molecules. so increasing total pressure increases yield of products
• changing total pressure affects the equilibrium position when there is a change in the total number of molecules on either side of the reaction
• what happens when pressure increases on a gas phase?

  • reaction will increase the rate at which equilibrium is reached
  • more collisions between molecules
  • increasing temperature increases rate at which equilibrium is attained
• Kp?


  equilibrium expression linking the partial pressure of a reactants and products at equilibrium
• partial pressure?


  the pressure it exerts in a mixture of gases if it occupied the container on its own
• total pressure = sum of the partial pressures
• partial pressure equation?


  total pressure x mole fractions
• mole fraction equation?


  number of moles in gas A / total number of moles of gas
• what happens if there is an increase in temperature?

  equilibrium moves in the endothermic direction to reverse the change
• what happens if there is a decrease in temperature?

  equilibrium moves in the exothermic direction to revers he change
• what happens in exothermic reactions in forward directions?

  increasing the temperature shifts equilibrium from right to left. value of Kp will decrease
• what happens in endothermic reactions in forward directions?

  increasing the temperature shifts the equilibrium from left to right. value of Kp will increase
• what happens when pressure increases?

  equilibrium shifts in the direction that produces the smaller number of molecules of gas to decrease the pressure
• what happens when pressure decreases?

  equilibrium shifts in the direction that produces the larger number of molecules of gas to increase the pressure
• mole fraction?


  portion of a gas mixture that is made up of particular gas
• what does changing temperature do to equilibrium?

  
  

  it changes how much product is formed at equilibrium which changes the mole fractions of the gases present, which changes their partial pressure