Equilibrium

State of the system:

• Described by stating the equilibrium pressure of water vapor at the given temperature

  • With constant volume and temperature, the partial pressure of each gas should be proportional to the number of moles of that gas

• Reactions are reversible - forward and reverse reactions take place at the same rate

Equilibrium Constant:

• The relationship between the partial pressures of different gases present at equilibrium

  • Equilibrium constant expression:

    

  • If K>1, that means products are favored

  • If K<1, that means reactants are favored

• Reciprocal Rule: the equilibrium constants for the forward and reverse reactions are the reciprocals of each other (K=1/K)

• Rule of multiple equilibria: If the reaction can be expressed as a sum of 2+ reactions, K for the overall reaction if the product of equilibrium constants of individual reactions

• Only temperature affects K

• We cannot tell reaction rate or enthalpy from K

Reaction Quotient (Q):

• Measures the beginning reactants and products, whereas K is measuring R and P after the equilibrium

  • The form is the same as that for the equilibrium constant, K

  • If Q was big and K is small, then the reaction would go backward (P—>R)

  • If Q and K were around the same (both big or both small) then there would be no/little change

  • If Q was small and K is big, then the reaction would go forward (R—>P)

Equilibrium:

• when rates of forward and reverse reactions and equal

• Forward and reverse reactions occur at the same rate

• The concentration of species remains constant with time and they are independent of the direction from which equilibrium is approached

End Point: