1. CE 3231 - Introduction to Environmental Engineering and Science Readings for Next Class : Section 2.4 O hio N orthern U niversity Introduction Chemistry, Microbiology & Material Balance Water & Air Pollution Env Risk Management Equilibrium and Kinetics How far and how fast a chemical reaction occurs makes all the difference. In today’s class we will cover the basics for writing and solving equilibrium and kinetic relationships. I will also introduce reaction order and solutions for common reaction order systems of equations.

2. Lecture 5 Equilibrium & Kinetics (Chemistry II)

3. Reactions Equilibrium Relationships

4. Reactions Rates of Reaction

5. Reactions Reaction Order Reaction rates for different reactions often follow similar mathematical forms, including: – Zero Order – First Order – Second Order These you can solve by hand…more complex forms require advanced mathematics

6. Reactions Reaction Order

7. The following table is a summary of important information related to 0, 1st and 2nd order reactions: Orderrate expression conc-time relationshiphalf-lifelinear plot 0rate = k X 0 - X = k X 0 /2k X vs t 1 rate = kX log X 0 /X = kt/2.30 0.693/k log X vs t 2rate = kX 2 1/x - 1/X 0 = kt 1/X 0 k 1/X vs t

8. Example Problems Following a reaction that has reached equilibrium 0.25 mols of N 2 gas and 0.43 mols of O 2 are left in a 1 L cylinder that contains 6.64x10 -3 mols of nitric oxide gas. Assuming that one mol of N 2 and one mol of O 2 react to form 2 mols of NO what is the equilibrium constant for this system? For the reaction: PCl 3 + Cl 2 ↔ PCl 5 … What is the equilibrium concentration of the product, PCl 5, if the initial concentrations of the reactants are [PCl 3 ] = [Cl 2 ] = 0.14 M and [PCl 5 ] o = 0 given K = 96.2 M -1