reversible reactions

• reversible reactions will reach...

  equilibrium
• equilibrium


  a state in which the rate of the forward reaction equals the rate of the backward reaction
• as reactant react, their concentrations...

  fall - so the forward reaction will slow donw
• as more products are made, their concentrations...

  rise - so the backward reaction will speed up
• what is happening at equilibrium?

  both reactions are still happening, but there's no overall effect - this means the concentrations of reactants and products have reached a balance and won't change
• equilibrium is only reached if...

  the reversible reaction takes place in a closed system
• what is a closed system

  a system where neither matter nor energy can enter or leave
• the position of equilibrium can be...


  on the right or on the left
• if equilibrium lies to the right...

  the concentration of the products is greater than the reactants
• If the equilibrium lies to the left...

  the concentration of the reactants is greater than the products
• in reversible reactions if the reaction is endothermic in one direction...

  it will be exothermic in the other
• the energy transferred from the surroundings by the endothermic reaction is equal to...

  the energy transferred to the surrounds during the exothermic reaction
• what does the position of equilibrium depend on?

  temperature, pressure (only affects equilibria involving gases), concentration
• if a change is made to the closed system...

  the system will act to counter that change
• Le Chatelier's Principle


  states that if a stress is applied to a system at equilibrium, the system shifts in the direction that relieves the stress.
• what happens to the equilibrium if temperature is increased?

  it will shift to the endothermic reaction

  - system acts to decrease temperature
• what happens to the equilibrium if temperature is decreased?

  it will shift to the exothermic reaction

  - system acts to increase temperature
• what happens to the equilibrium if pressure is increased?

  it will shift to the side with less moles of gas

  - system acts to decrease pressure
• what happens to the equilibrium if pressure is decreased?

  it will shift to the side with more moles of gas

  - system acts to increase pressure
• true or false? changing the pressure will always change the position of the equilibrium for a reversible reaction


  false

  - changing the pressure only affects an equilibrium involving gases

  - equilibrium will not shift if there are an equal number of gas molecules on each side
• 1 mole of gas =

  24000 cm³
• what happens to the equilibrium if concentration of reactants is increased?

  it will shift to the side with the products

  - system acts to decrease reactant concentration
• what happens to the equilibrium if concentration of reactants is decreased?


  it will shift to the side with the reactants

  - system acts to increase reactant concentration
• what happens to the equilibrium if concentration of products is increased?

  it will shift to the side with the reactants

  - system acts to decrease product concentration
• what happens to the equilibrium if concentration of products is decreased?

  it will shift to the side with the products

  - system acts to increase product concentration