Factors which Affect Chemical Equilibrium Le Chateliers Principle –Projects Direction of Change N 2 (g) + 3H 2 (g) ↔ 2NH 3 (g)

Problem The following equilibrium is established. 2NaHCO 3(s) ↔ Na 2 CO 3 ( s) + H 2 O (g) + CO 2 (g) What would happen to the equilibrium position if: (a)Some of the CO2 were removed from the system; (b)some solid Na2CO3 were added to the system; (c ) some of the solid NaHCO3 were removed from the system

Chapter 14: Values of K Factors which Affect Equilibrium “K” Values are temperature dependent

LeChatelier’s Principle: Temperature Values of “K” are temperature dependent Endothermic Reactions –A + B + (heat energy)  C + D Exothermic Reactions –A + B  C + D + (heat energy)

Chapter 14: Values of K (2) A Value can give Position of Equilibrium k = products/reactants If K ≈ 1 product amounts ≈ reactant amounts If K >1 More products than Reactants If K< 1More Reactants than Products

Values of K Some Values of K are Given Below. Kc = 9.5E-13 Kc = 9.5E-14 Kc = 9.5E5 Kc = 9.5E1 (a) Which value represents the formation of the smallest amount of product? (b) Which value represents the formation of the largest amount of product?

CALCULATIONS OF VALUES OF “K” 1. First Write “K” expression. 2. Must have exact equilibrium concentrations.

Problem Gaseous Hydrogen iodide is placed in a closed container at 425 Celsius degrees where it is partially decomposed to hydrogen and iodine: 2HI (g) H 2(g) + I 2(g). At equilibrium, it is found that [HI] =3.53E-3 M; [H 2 ]=4.79E-2 M; [I 2 ]=4.79E-2 M. Calculate Kc.

Problem A mixture of moles of NO, moles of H2, and 0.10 moles of H 2 O is placed in a 1.0 liter vessel. The following equilibrium is established: 2NO(g) + 2H 2(g) N 2(g) +2H 2 O (g) At equilibrium, [NO]= M. (a) Calculate the equilibrium concentrations of H 2, N 2, and H 2 O. (b) Calculate Kc

Chemical Equilibrium: LeChatelier’s Principle LeChatelier’s Principle 2NOBr (g)  2NO (g) +Br 2(g)

Chemical Equilibrium: LeChatelier’s Principle & Temperature Consider the following equilibrium for which ▲H < 0 2SO 2(g) + O 2(g)  2SO 2(g) How will each of the following changes affect an equilibrium mixture of the three gases.

Problem 2SO 2(g) + O 2(g)  2SO 2(g) ▲H < 0 (a) O 2(g) is added to the system (b) the reaction mixture is heated (d) a catalyst is added to the mixture (f) SO 3(g) is removed from the system.