Reversible Reactions and Equilibrium

Reversible Reactions Reactions that run in both a forward (left to right) and reverse (right to left) direction Typically these reactions are in a closed system Typically conditions such as temperature are kept constant Need a double arrow > to indicate that its reversible and not just one way

Chemical Equilibrium Point where the forward and reverse reactions are occurring at the same rate As products are formed, those products breakdown and create reactants that can re-form products DOES NOT MEAN 50/50 but refers to rate and concentration only Concentration of reactants and products remain CONSTANT at this point

LeChatliers principle States that any equilibrium reaction will do what is necessary to get back to equilibrium if we change one of the conditions of the reaction (Concentration, temperature pressure) Equilibrium systems want to remain constant Systems must be closed so that the adjustment can occur

Rules for Shifts 1. Too much of something……shift away from it to use it up and get back to the equilibrium position/concentration 2. Take away something…..shift towards that so we can fill it back in and get back to equilibrium position/concentration

Directional Shifts 1. Too much on the right-----shift LEFT 2. Not enough on the right-----shift RIGHT 3. Too much on the left ----- shift RIGHT 4. Not enough on the left----shift LEFT 5. Catalysts NEVER Shift equilibrium, they just speed things up

Rules for Pressure Changes 1. Count the number of moles of GASES ONLY!!! On each side of the equation 2. If the Pressure INCREASES ---- the shift is to the side with LESS MOLES of gases, to spread out energy and maintain the equilibrium position 3. If the Pressure DECREASES --- the shift is to the side with MORE MOLES of gases, to favor the side with more collisions and to possibly get back to equilibrium. 4. If BOTH SIDES ARE EQUAL – NO Shift Occurs