CP A Thermodynamic Process in a Solid. A cube of copper

Chemistry of Solutions Lecture no. 7 Thursday, September 15, 2016 Topics Covered: Le Châtelier’s principle, the nature of acids and bases, acid strength, the pH scale, and calculating the pH of strong acid solutions. Le Châtelier's Principle If a change is imposed on a system at equilibrium, the position of the equilibrium will shift in a direction that tends to reduce that change. A chemical reaction is not a sentient being, if a substance is added the rates of the forward and reverse reactions are disturbed. The net reaction occurs in one direction, until the system reaches equilibrium again, At the new equilibrium position, the reactants and products have different concentrations (compared to their initial concentrations). 1. Changing concentrations: disturbing a system’s equilibrium position by adding a substance causes the reaction to shift in the direction that absorbs some of the added substance. If a substance is removed from an equilibrium system, the reaction will shift in the direction that produces more of the lost substance. Note: adding noble gases or solids to a gaseous equilibrium system does not disturb its equilibrium position! Adding a noble/inert gas only changes the total pressure of the system, not the partial pressures of each species. The same rule applies if you add a substance that won't react with any of the chemical species in the reversible reaction. 2 2. Changing Pressures (gaseous systems): the pressure of a gaseous s