chapter18_emmo

__**Chapter**__ **__18: Chemical Equilibrium__** When these reactions have the same reaction forwards and reverse, the reaction is at equilibrium.
 * Some reactions are reversible.


 * This does not mean that there are 50/50 mix of products and reactants.

pA+qB <=> rC+sD Keq= __[products]__ = __[C]r [D]s__ [reactants] [B]q [A]p
 * __Mass Action Expression__**


 * If Keq = 1, there is an equal concentration of products and reactants.[[image:http://etc.usf.edu/clipart/36300/36340/seesaw_36340_lg.gif width="170" height="70" caption="Equation at Equilibrium"]]
 * If Keq>1, there are more products than reactants. The equilibrium "favors" the products.
 * If Keq<1, there are more reactants than products. The equilibrium "favors" the reactants.
 * Keq equations only include GAS and AQUEOUS compounds. If a compound is solid, do not include it in the equation.

Practice problems: ~2NO2 (g) <=> N2O4(g) Give the Keq.

~N2 +3H2 <=> 2NH3 Give the Keq.

If an equilibrium is stressed, the reaction will shift in such a way as to minimize the stress. *If you add more reactants to the equation, then the equation will shift to the right.
 * __LeChatelier's Principle (LCP):__**
 * If you add more product to the equation, then the equation will shift to the left.

__**Pressure Change:**__ Example: ~CH3OH <=> 2H2 +CO. Increase the pressure. Which direction does the equation move? ~3O2 <=> 2O3 What happens if you decrease the pressure?
 * If pressure is increased, thne the reaction moves to the smaller side (the side with fewer moles).
 * If the pressure is decreased, then the reaction moves to the side with more moles.

NaCl(s) <=> Na+(aq) + Cl- (aq) Ksp=[Na+][Cl-] What will happen if CaCl2 is added? CaCl2 <=> Ca2+ +2Cl- Cl is the common ion, because it is the ion common between the two equations.
 * __Solubility Product:__**

Answers: ~Keq = __[N2O4]__ [NO2] ~Keq= __[NH3]2__ [N2][H2]3 ~The equation moves to the left. ~The equation will move to the right.