if Q > K The reverse reaction will occur until equilibrium is achieved.
if Q < K The forward reaction will occur until equilibrium is achieved.
Achieving equilibrium is a driving force in chemical systems and will occur when possible. It cannot be stopped (spontaneous)
1.For the equilibrium system, 2NO 2 (g) N 2 O 4 (g), the equilibrium constant, K C, is 8.8 at 25 0 C. If analysis shows that 2.0 x 10 -3 mole of NO 2 and 1.5 x 10 -3 mole of N 2 O 4 are present in a 10.0 L flask, is the reaction at equilibrium?
Types of Reactions 1. one way (goes to completion) NaOH (s) Na + (aq) + OH - (aq)
Types of Reactions 2. Equilibrium (two opposite reactions at same time) a. dimerization 2NO 2 (g) N 2 O 4 (g)
b. dissociation of a weak electrolyte CH 3 COOH + H 2 O CH 3 COO - + H 3 O +
c. saturated aqueous solutions AgCl (s) Ag + (aq) + Cl - (aq) C 6 H 12 O 6 (s) C 6 H 12 O 6 (aq)
2.When 2.0 moles of HI(g) are placed in a 1.0 L container and allowed to come to equilibrium with its elements, it is found that 20% of the HI decomposes. What is K C and K P ?
Applications of the Equilibrium Constant & LeChateliers Principle
3.0.017 mol of n-butane is placed in a 0.50 L container and allowed to come to equilibrium with its isomer isobutane. K C at 25 0 C is 2.5. What are the equilibrium concentrations of the two isomers?
Set up an ICE table Initial [ ] of components Change in [ ] Equilibrium [ ]
n-butane isobutane I 0.034 0 C -x +x E 0.034-x x
4.2.0 mols Br 2 are placed in a 2.0 L flask at 1756 K, which is of sufficient energy to split apart some of the molecules. If K C = 4.0 x 10 -4 at 1756 K, what are the equilibrium concentrations of the bromine molecules and atoms?
Change T – change in K – therefore change in P or concentrations at equilibrium Use a catalyst: reaction comes more quickly to equilibrium. K not changed. Add or take away reactant or product: –K does not change –Reaction adjusts to new equilibrium position Le Chateliers Principle