CHEM 1212 1nd Edition Lecture 6 Outline of Last Lecture I. Colligative PropertiesII. ColloidsOutline of Current Lecture I. Rates of Chemical ReactionsII. Reaction Conditions and RateIII. Effects of Concentration on Reaction RatesIV. Rate EquationsV. The Order of a ReactionVI. The Rate Constant kVII. Determining a Rate EquationCurrent LectureI. Rates of Chemical Reactionsa. Chemical Kinetics: a study of the rates of chemical reactionsb. Reaction Mechanism: the detailed pathway taken by atoms and molecules as a reaction proceedsc. Rate of reaction = Change in concentrationChange in timed. Average rate of reaction = Δ concentration Δtimee. Example: N2O5  2NO2 + ½ O2i. Rate of reaction = - Δ[N2O5] Δtii. The minus sign is there because the concentration of this compound decreases over time, and rate is always expressed as a positive quantityiii. (Data table for this problem given on pg 670)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.iv. Rate = - (1.10 mol/L) – (1.22 mol/L) = + 0.12 mol/L55 min – 40 min 15 minRate = 0.0080 mol N2O5 consumedL x minf. Rates based on changes in concentrations of products will have a positive sign because concentration is increasingg. The longer after the reaction has begun, the slower the rate will beh. We can find the instantaneous rate at a single point in timeII. Reaction Conditions and Ratea. Effects of Concentration and Temperaturei. If the concentration of a reactant is increased, the reaction rate will often increase as wellii. Chemical reactions occur more rapidly at higher temperaturesb. Catalysts: substances that accelerate chemical reactions but are not themselves consumedc. The surface area of a solid reactant can also affect the reaction ratei. Only molecules at the surface of a solid can come into contact with other reactantsii. The smaller the particles of a solid, the more molecules are found on the solids surfaceIII. Effect of Concentration on Reaction Ratea. We determine how concentration affects reaction rate by observing the reaction rate when concentrations are variedb. Effect of concentration is different for different reactionsIV. Rate Equationsa. Rate equation or rate law: expresses the relationship between reactant concentration and reaction rateb. Rate equation = k[A]m[B]ni. The rate equation expresses that the rate of reaction is proportional to the reactant concentrationii. Catalysts in reactions are included in the rate equationV. The Order of a Reactiona. Overall reaction order: sum of the exponents on all concentration termsb. Example: 2NO(g) + Cl2(g)  2NOCl(g)i. Rate equation = k[NO]2[Cl2]ii. NO – second orderiii. Cl2 – first orderiv. Overall reaction order = (first + second order) = third orderVI. The Rate Constant ka. K – proportionality constant that relates rate and concentration at a given temperatureb. Enables you to find the reaction rate for a new set of concentrationsc. Units of ki. First-order reactions: 1/timeii. Second order reactions: L/mol x timeiii. Zero-order reaction: mol/L x timeVII. Determining a Rate Equationa. Method of initial rates (one way to determine rate equation)b. Initial rate is the rate of the reaction when