Lecture 12 (2/4/13)
• Types of Equilibria:
o Homogeneous equilibria:
Equilibria involving reactants and products in the same phase.
Mostly gas phase in Ch. 16; aqueous solutions in Ch. 17
o Heterogeneous equilibria:
Equilibria involving reactants and products in more than one
phase, e.g., decomposition of a solid that produces a gas.
• Heterogeneous Equilibria:
o CaCO (s)3⇌ CaO(s) + CO (g) 2
o Concentrations of solids are constant at a given
Density (g/L) = mol = (M)
Molar mass (g/mol) L
• Le Châtelier’s Principle:
o “A system at equilibrium responds to a stress in such a way that it relieves
o Factors that will change the relative rates of forward/reverse reactions, or
change the value of Q compared to K, will cause a shift in the position of
• Concentration Stress:
o H O(2) + CO(g) ⇌ H (g) 2 CO (g) 2
o Remove CO (g):2
Rate of reverse reaction decreases; reaction proceeds in forward
direction to establish new equilibrium.
o Q compared to K:
Removing CO , 2 > Q; reaction shifts