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Chemistry (160)
CHM 2045 (77)
chu (15)
Lecture

# 5____

3 Pages
130 Views

School
University of Florida
Department
Chemistry
Course
CHM 2045
Professor
chu
Semester
Spring

Description
10  o F. • Reaction Rate Equations o A. Rate of a reaction says how quickly [product] or [reactant] is changing o B. Given in molarity per second, mol/L*s o C. Factors affecting reaction rates:  1. Temperature  2. Pressure – usually negligible  3. [substances] • Reaction mechanisms o A. How the molecules collide • Reaction order o A. Reaction order = sum of all exponents of the concentration variables in the rate law. o B. Reaction order in A = the exponent of [A] • Reaction rates o A. Depends on multiple factors • Rate constant o A. The k in the rate law is the rate constant. o B. The rate constant is an empirically determined value that changes with different reactions and reaction conditions. o C. Within a given equation:  1. Independent of: • a. [product] • b. [reactant]  2. Dependent on: • a. Temperature • b. Catalyst • Rate law o A. The equation that describes the rate = the product of reactants raised to some exponents • Equilibrium constant o A. The balance of products and reactants at equilibrium   10    11  • Reaction Rate Equations: Example o A. aA + bB  cC + dD o B. Lower case letters are stoichiometric coefficients • Reaction Rate Equations: Types o A. Molecularity: the number of molecules colliding at one time to make a reaction o B. Elementary Reaction: occur in a single step; only here can the coefficient of the balanced equation serve as the exponent in the rate law o C. Unimolecular: one molecule colliding o D. Bimolecular: two molecules colliding o E. Termolecular: three molecules colliding • Reaction Rate Equations: Intermediates o 1. Intermediates: species that are products of one reaction and reactants of a later reaction in a reaction chain o 2. Concentrations are often very low because they are both unstable and used up quickly • Reaction Rate Equations: Directions o 1. Reaction rates are reversible; that is, as products are formed, products begin to react to form reactants • Reaction Rate Equations: Rate Law o A. Rate law: considering the forward reaction only o B. Rateforward kƒ[A] [B]β o C. k ƒ rate constant for the forward reaction o D. α and β = order of each respective reactant o E. α + β = overall order of the reaction • Rate Law Experimental Determination Trial [A] (M) [B] (M) r (M/sec) initial initial initial 1.00 1.00 2.0 1 1.00 2.00 8
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