CHM 104 1st Edition Exam 1 Study Guide Lectures 1 9 Lecture 1 January 26 Math Review Syllabus Lecture 2 January 28 What is chemical kinetics and rate How do you determine the rate of change of chemical concentrations Chemical Kinetics is the study of chemical change with time to determine how a reaction occurs Over time the reactant concentration decreases and the product concentration increases The rate of change of chemical concentrations measured over a specific time and interval Rate of reaction is always expressed as a positive number aA bB cC dD Lecture 3 January 30 What are the effects of concentrations on reaction rates What is the rate constant What is the importance of the reaction order A Products Rate k A n Exploring values of n A M 1 2 n 0 n 1 n 2 0 0 100 Time s n 0 or zeroth order rate is independent of reactant rate k A 0 A 0 1 rate k no change in rate as A decreases slope gives you a way to directly determine rate constant Rate k unit k M s n 1 or first order rate directly proportional to reactant rate k A 1 as A decreases the rate slope decreases Rate k A 1 unit k 1 s n 2 or second order rate directly proportional to the square of reactant as A decreases the rate slope decreases Rate k A 2 unit k 1 Ms Lecture 4 February 2 How do you use the integrated Rate Laws and half life equations Integrated Rate Laws A Products Rate k A n0 Sometimes reactions are characterized by life the time it takes reactant to decrease by 50 Zero Order First Order Second Order Lecture 5 January 4 What is the Arrhenius Equation Temperature dependence is contained in k which is only at constant temperature The relatively between k and T was quantified by Swedish chemist Svank Arrhenius Arrhenius Equation K A x e Ea Rt How do we determine Ea and A for a chemical reaction Ea and A can be determined by measuring k at 2 different temperatures Lecture 6 January 6 What is a reaction mechanism and why is it important Reaction Type Molecularity Rate Law Equation A Products unimolecular 1 A A Products bimolecular 2 A B Products bimolecular 2 A A A Products termolecular 3 A B B Products termolecular 3 1 2 k A B A B C Products termolecular 3 1 1 1 k A B C k A k A 1 2 1 1 k A B k A 3 Each step in the mechanism has its own rate law equation and rate constant Usually one step will be much slower than all of the other steps rate limiting determining step Evaluation a Mechanism 1 2 3 4 Elementary steps of the proposed m If both criteria are met then the reaction might happen that way Mechanism must add up to overall reaction Rate Law equation for the proposed mechanism must match that observed by experiment data Lecture 7 January 9 What is homogeneous and heterogeneous catalysis What is a catalyst Rate k2 N2O2 1 H2 1 To compare to exponentially determined rate law we need to rewrite in an equivalent for our intermediate need rate law without intermediate present Strategy A lot of N2O2 will build up causes the reverse process to speed up Equilibrium eventually reach a point where NO is formed as fast as N2O2 is formed Rate step 1 forward rate step 2 backward Catalyst substance that increases reaction rates by providing different reaction mechanism which has a lower activation energy Catalysts are recycled Homogeneous catalysts are used in 1 step and regenerated in another step and heterogeneous catalysts are a platform for molecules to come together Lecture 8 January 11 What is chemical equilibria Rate at equilibrium forward Rate at equilibrium reverse Law of Mass Action aA bB cC dD Reverse the equation inverse K Multiply the coefficient in the reaction by a factor of n raise K to power of n Add 2 reaction with known K values together multiply the K values together Lecture 9 January 13 What is heterogeneous equilibria and equilibrium calculations The equilibrium equation can be written using molarity or partial pressures gases The pressure of the gas is proportional to molarity PV nRT aA bB P n v RT cC dD If c d a b 0 P eq RT Kp Kc RT c d a b Kp Kc All are concentrations AFTER an equilibrium has been established Pure solids and liquids are replaced by 1 s their concentrations DON T depend on the container volume just the density of the substance Equilibrium Calculations K can be calculated if ALL equilibrium concentrations are known If K is known then equilibrium can be determined