Chemistry 104 Kinetics Questions and Answers: Reaction Rates, Rate Laws, and Catalysts, Exams of Chemistry

Download Chemistry 104 Kinetics Questions and Answers: Reaction Rates, Rate Laws, and Catalysts and more Exams Chemistry in PDF only on Docsity! Chem 104 Kinetics Questions And Answers 4 factors that contribute to/change reaction rate - correct answer 1) concentration 2)reactant phase 3)temperature 4)catalyst if their is a plot of concentration over time of the reaction A--> 2B+C.Describe what the graph would look like. - correct answer A's slope would be exponentially negative since it is a reactant. Both B and C's slope would be exponentially positive since they are both products but Bs slope/line would be 2x C's due to coefficients. Steps To determine the initial rate from a graph - correct answer 1) Find a point on line and then another point close to it 2)find slop of those two points how do you find instantaneous rate? - correct answer take the slope of the line tangent to the point Chem 104 Kinetics Questions And Answers how do you find average rate? - correct answer take the slop of the two points (the certain start point and the certain end point that are given to you) Steps to writing a rate expression - correct answer 1) write delta molecule/delta Time 2) add - sign for reactants and + sign for products 3)use coefficients to form ratios 4) set all expressions equal to each other Writing a rate law - correct answer rate=k[A]^x[B]^y where: rate is the initial rate of reaction k is the constant (slope of linear line) A and B are reactants x and y are the order of each reactant (0,1,2 or 3) Chem 104 Kinetics Questions And Answers method of intial rates: determining order of reaction - correct answer For each individual reactant compare to initial rate when other reactants remain the same method of initial rate: writing the rate law - correct answer rate=k[A]^x[B]^y where A and B are reactants and x and y are the order of reactants and k is the rate constant method of Initial rate: calculating the rate constant - correct answer use the data from the data table plug in data to equation rate=k[A]^x[B]^y solve for k by rearranging the equation to: k=(rate)/([A]^x[B]^y) Chem 104 Kinetics Questions And Answers Method of Initial rate: determination activation energy - correct answer ln(K2/k1)=Ea/R (1/T1-1/T2) Ea=Rx(ln(k2/k1)/1/T1-1/T2) Analysis of integrated rate - correct answer [A]t=-kt+[A] 0 0 order ln[A]t=-kt+ln[A]0 1st order 1/[A]t=kt+1/[A]0 3rd order Analysis by integrated rate:to find reaction rate - correct answer Plot 3 different graphs and see which one is linear if ([A]t vs t 0 order ln[A]t vs t 1st order 1/[A]t vs t 2nd order Analysis of integrated rate: what does the slope of the linear line indicate - correct answer 0 order=0 1st order=-Kobs 2nd order=-Kobs Chem 104 Kinetics Questions And Answers Analysis by integrated rate: how do you find the order of reaction of B - correct answer b=(ln(kobs2)-ln(kobs1))/(ln[B]2- ln[B11) (The answer will give you the order of B) Analysis by integrated rate: to find rate constant k - correct answer kobs=K[B]^b solve for k=B^b/kobs Analysis by integrated rate: how to find/solve for activation energy - correct answer Ea=R x (ln(k2/k1)/(1/T1-1/T2)) R=(8.314 J mol^-1 K^-1) Method of instantaneous rate flow chart: is plot of rate vs A linear? if yes what? if no what? - correct answer if yes: ask question does slope=0? if no reaction is NOT 1st order in[A] (we only know x does not = 1) Chem 104 Kinetics Questions And Answers analysis by half life: half life trends for 1st order - correct answer constant analysis by half life: half-life trend for 2nd order - correct answer increases half life equation for zero order - correct answer t1/2=[A]0/2k half life equation for first order - correct answer t1/2=0.693/k (0.693 aka ln2) half equation for second order - correct answer t 1/2= 1/k[A]0 rate law for the reaction is the same as what in a multi mechanism reaction - correct answer the rate limiting step aka the slow step a mechanism ____ be supported but ______ be proven - correct answer can Chem 104 Kinetics Questions And Answers cannot the rate limiting step for a catalyst mechanism has a ______________ activation energy and therefore is ______________ than the uncatalyzed reaction - correct answer lower faster homogeneous catalyst - correct answer a catalyst that exists in the same physical state as the reaction it catalyzes enzyme - correct answer a highly efficient catalyst for one or more chemical reactions in a living system How do the initial and final energies differ in a catalyzed reaction and an uncatalyzed reaction? - correct answer they don't, they are the same because even though the mechanisms are different their and initial and final energies remain the same Chem 104 Kinetics Questions And Answers what are the most efficient catalyst - correct answer enzymes Cofactors - correct answer inorganic or organic molecules or ions that need to be present for an enzymes catalytic activity to be fully available substrate - correct answer reactant of an enzyme-catalyzed reaction Active site of an enzyme - correct answer the region of an enzyme that attaches to a substrate induced fit - correct answer the change in shape of either enzyme, substrate or both molecules when they bind reactions that involve catalyst have two important properties - Chem 104 Kinetics Questions And Answers nonmolecular - correct answer any reaction that has more then two reactants in any combo steric factor - correct answer the factor (always less than 1) that reflects the fraction of collisions with orientations that can produce a chemical reaction. steric factors in symmetrical molecules vs asymmetrical molecules - correct answer All collision with symmetrical atom could be effective if they have enough energy. However, collisions with the "wrong end" of a asymmetrical molecule may be ineffective because of the atoms it came into contact during the collision Steps to analyzing a multi mechanism reaction - correct answer 1) add all steps together to find balanced chemical equation note: cancel out all intermediates note: catalyst are NEVER part of chemical equation 2) Find rate law of slow step mechanism Chem 104 Kinetics Questions And Answers 3) check to see if there are any intermediates in rate law of slow reaction if there isn't: then this rate law is the overall equation rate law if there is: 4) use rate laws of fast step to find an equation that you can use to substitute for the intermediate in rate law of slow step 5) substitute for intermediate in slow step rate law 6) find overall rate law