Do Now 1.What is reaction rate? 2.What does the term “equilibrium” signify? Can you describe physical changes in the chemistry lab where equilibrium is achieved? 3.When calculating the mass of product produced using stoichiometry, what assumption do you make about the amount of reactant you started with? 4.What is meant by chemical equilibrium? 5.Which components of the reaction (reactants/products) are present at this point? 6.What happens to the concentrations of those species once equilibrium is established?

Two opposing chemicals reactions occur at the same rate: H 2(g) + I 2(g) 2HI (g) Chemical Equilibrium Forward: H 2(g) + I 2(g) -> 2HI (g) Reverse: 2HI (g) -> H 2(g) + I 2(g)

Will we able to use stoichiometry to predict amount of materials that will be produced?

N 2(g) + 3H 2(g) 2NH 3(g) N 2 H 2 NH 3 Exp1: Initially 1.0 M1.0 M 0 Exp 2: Initially M Exp 3: Initially2.0 M1.0 M3.0M At equilibrium 0.921M0.763M0.157M At equilibrium 0.399M1.197M0.203M At equilibrium 2.59M2.77M1.82M

Law of Mass Action The ratio of product concentrations to reactant concentrations at equilibrium is constant. Origin is in thermodynamics but we can look at kinetics. For reaction A + 2B AB 2 What is the rate law for the forward and reverse reactions? What happens when equilibrium is established?

The equilibrium constant, K for the reaction H 2(g) +F 2(g) 2HF (g) has the value of 2100 at a particular temperature. When the system is analyzed at equilibrium at this temperature, the concentrations of H 2 and F 2 are both found to be M. What is the concentration of HF in the equilibrium system under these conditions?

What does the size of K indicate Extent to which a reaction proceeds to completion 2O 3 3O 2 K=1 x HF H 2 + F 2 K=1 x N 2 +3H 2 2NH 3 K=10

1.00 moles of dinitrogen trioxide is placed into a 2.0 L flask at 25ºC and 1 atm and it decomposes into nitrogen dioxide and nitrogen monoxide reversibly. Write an equation to describe this reversible gas phase reaction What is the composition of the reaction mixture at equilibrium if it contains 0.30 moles of nitrogen dioxide? What is the value of the equilibrium constant, K?’

The formation of hydrogen fluoride from hydrogen and fluorine has an equilibrium constant of 115 at a certain temperature. Write a reversible reaction and an equilibrium expression. In a particular experiment 3.00 moles of each component is added to a 1.50 L flask. Calculate the equilibrium concentrations of all species.

How are concentration and pressure of a gas related? Write the equilibrium expression for the reversible decomposition of calcium carbonate. (Predict the products). Write states. What is Kp?

For which of the following reversible reactions is K equal to Kp? A. Homogeneous reaction of ammonia with oxygen to produce nitrogen and water. B. Aqueous hydrogen peroxide breaks down into liquid water and gaseous oxygen. C. Homogeneous gas phase synthesis reaction of hydrogen and bromine.

For the reaction: 2NO (g) N 2(g) +O 2(g) the equilibrium constant is 2400 at a certain temperature. For which of the following sets of conditions is the system at equilibrium? For those that are not at equilibrium, in which direction is the reaction proceeding toward equilibrium. A) 1.0 L flask contains 0.24 mole NO, 2.0 mol N 2, and 2.6 mole O 2 B) 2.0 L flask contains mole NO, 0.60 mol N 2, and 4.1 mole O 2 C) 1.0 L flask contains mole NO, 4.4 mol N 2, and 3.7 mole O 2

Reaction quotient, Q A tool used to determine if a reaction is at equilibrium Insert any concentrations you have and find the quotient, Q Compare to the K, the equilibrium constant.

What is Le Châtelier’s Principle? If a stress is applied to an equilibrium system, the reaction will shift in a direction that tends to reduce the change.

N 2(g) + 3H 2(g) 2NH 3  H =-92 kJ StressShift[N 2 ][H 2 ][NH 3 ] Add N 2 Remove NH 3 Increase Temperature Increase Pressure( by decreasing V) Add catalyst Increase Volume Add acid (NH 3 is a base) Will K change?