$course$/Kinetics CompareEnergyProfile01 Consider the following reactions that take place at the same temperature, begin with the same molar concentrations, and whose energy profiles are presented below: ]]> Remember, a larger activation energy means a slower reaction which must have a smaller rate constant. 1 0.1 0 1 Which reaction is endothermic? Reaction I Which reaction has the higher activation energy? Reaction II Assuming equal Arrhenius A factors, which reaction is faster? Reaction I Which of the reactions has a larger rate constant? Reaction I Reaction I and Reaction II neither Reaction I nor Reaction II ConcVsTimeGraph01 The following graph shows the change in concentration as a function of time for the reaction:
2NO2(g) + F2(g) 2NO2F(g)
What do each of the curves A, B, and C represent?
]]> The analysis of this question involves thinking about the relationship between reactants disappearing and products appearing. It also involves looking at the coefficients of the balanced equation to decide the relationship between the concentrations. 1 0.1 0 0 2]]> B 2]]> C 2F]]> A Enzyme01 Trypsin assists in digestion by breaking proteins down into smaller peptides. However, this process is not as efficient in the presence of fluorophosphates. Identify the role of each of these components.]]> An enzyme is a protein that is a highly efficient catalyst for one or more chemical reactions in a living system. A molecule whose reaction is catalyzed by an enzyme is referred to as a substrate. An inhibitor is a molecule that decreases the activity of an enzyme. 1 0.1 0 1 fluorophosphate inhibitor proteins substrate trypsin enzyme InterpretEnergyProfile01 Use the energy profile below to decide if the following statements are true or false.
]]> To determine whether a reaction is exothermic or endothermic, compare the energy of the products and the reactants. If the products have less energy than the reactants, some energy will transfer to the surroundings (exothermic reaction). The reaction may have more than one step. Each step is represented by a bump in the profile. The higher the bump the more energy a molecule needs in order to react and the slower the reaction at that step. To decide where products, reactants, intermediates, and transition states are located in the diagram, you need to think about how the molecules are transformed during a reaction. 1 0.1 0 1 This reaction is exothermic. True The reactants are represented by letter A. True The fastest step in this reaction is step D. False An intermediate is represented by letter C. False RxnOrder01 For the reaction below, determine the order with respect to each reactant and the overall order.
2NO2(g) + F2(g) 2NO2F(g)
rate = k[NO2][F2]]]> Rate = k[A]m[B]n
... where m is the order of A, n is the order of B etc. Note, if a reactant is not included in the rate equation then its concentration doesn't affect the rate and its order is zero. The overall order is the sum of the powers (m+n+...).]]> 1 0.1 0 0 2]]> first-order 2]]> first-order overall second-order zero-order third-order fourth-order RateConstantUnits01 3NC to CH3CN has a rate constant of 0.46 s-1 at 600 K.

(1) Based on the units of the rate constant, what is the order of the reaction? {1:MULTICHOICE:zero-order#No, that is not correct.~=first-order#Correct!~second-order#No, that is not correct.~third-order#No, that is not correct.}

(2) What is the concentration of CH3CN after 0.20 minutes of reaction if the initial concentration is 0.10 M? {1:NUMERICAL:=4e-4:1e-5#Correct!~%50%4e-4:5e-5#Close, but not quite.}(Do not include units!)

]]> k in units of time-1 tells us it is a first-order reaction. This in turn tells us we need to use the integrated rate law: ln[A] = -kt + ln[A]o.]]> 0 ArrheniusActEnergy01 The rate constant for the first-order dehydration of tert-butyl alcohol at 500oC is 1.20 x 10 -4 s -1. The rate constant for this process at 600oC is 6.80 x 10 -3 s -1. Calculate the activation energy for this reaction in kJ/mol. (R = 8.314 J/mol K)]]> 1 0.1 0 0 true false abc -227 kJ/mol 1 and k2. Be sure that each rate constant is matched correctly to its temperature.]]> 227 kJ/mol Correct! 318 kJ/mol Check your arithmetic carefully. If is easy to make an arithmetic error using this equation. 100. kJ/mol You used the temperature in degrees Celsius. You always need to use the temperature in Kelvin for calculations. -100 kJ/mol 1 and k2. Be sure that each rate constant is matched correctly to its temperature.]]> ArrheniusRateConst01 CH3CH2NO2 C2H2 + HNO2

Using the graph below, calculate the rate constant for this reaction at 40.0oC.
]]> 1 0.1 0 0 true false abc -18 sec-1]]> Correct. ln k = (slope) 1/T + intercept where the slope is -Ea/R and the intercept is lnA. -15 sec-1]]> Your answer does not match an obvious error, but it is incorrect. ln k = (slope) 1/T + intercept where the slope is -Ea/R and the intercept is lnA. -1]]> You left your temperature in Celsius. You have to convert the temperature to Kelvin to solve for the rate constant correctly. ln k = (slope) 1/T + intercept where the slope is -Ea/R and the intercept is lnA. 5 sec-1]]> You have not used the equation correctly. The equation for the line is ln k = (slope) 1/T + intercept where the slope is -Ea/R and the intercept is lnA, not k=(slope)T + intercept. You also need to convert the temperature to Kelvins. 6 sec-1]]> You have not used the equation correctly. The equation for the line is ln k = (slope) 1/T + intercept where the the slope is -Ea/R and the intercept is lnA, not k=(slope)T + intercept. ArrheniusTemp01 The activation energy for the isomerization of cyclopropane to propene is 274 kJ/mol. By what factor does the rate of reaction increase as the temperature rises from 500oC to 550oC assuming all else remains constant? (R = 8.314 J/mol k)

Hint: This is asking for the ratio of rates which is proportional to the ratio of the rate constants, all else being equal.

]]> 1 0.1 0 0 true false abc 1.0 3 J or 8.314 J to 8.314 x 10-3 10kJ]]> 13 Correct! 2.6 2/k1 = e 2.59]]> 2]]> You used the temperature in degrees Celsius. You always need to use the temperature in Kelvin for calculations. CatalystTrueFalse01 Check the box for each statement about catalysts that is true.]]> 1 0.1 0 0 false false abc An enzyme is a catalyst. Correct. The active site of an enzyme is specific and only binds certain substrates. Correct. Catalysts increase the rate of a reaction by altering the mechanism thereby increasing the activation energy. Catalysts increase the rate of a reaction by altering the mechanism thereby increasing the activation energy. CatalyticConverters01 Pollutant1970 Emissions1990 EmissionsCA ultra-low emissionsCxHy1.5 g/mile0.25 g/mile0.04 g/mileCO15 g/mile3.4 g/mile1.7 g/mileNOx3.1 g/mile0.4 g/mile0.2 g/mileCatalytic converters are used in automobiles to convert pollutants in engine emissions to benign products. Catalytic converters in today's automobiles are made of a porous ceramic brick that has been coated with catalysts, additives, stabilizers, and support materials. Corning has developed bricks that have very thin-walled channels with 600 channels per square inch. Which of the following research goals did they target?]]> 1 0.1 0 0 true false abc Catalytic converters need to have a high surface area. Correct. By having more channels, they have increased the surface area of the brick. Catalytic converters need to withstand rapid temperature fluctuations. By having more channels, they have increased the surface area of the brick. The catalyst has to last at least 100,000 miles. By having more channels, they have increased the surface area of the brick. The catalyst needs to be stable at high temperatures. By having more channels, they have increased the surface area of the brick. ElementaryRxnOrNot01 Which of the following reactions could be elementary and unimolecular reactions?]]> 1 0.1 0 0 false false abc ]]> Correct. A unimolecular elementary reaction is an elementary reaction in which one reactant molecule produces the product molecule or molecules. ]]> Correct. A unimolecular elementary reaction is an elementary reaction in which one reactant molecule produces the product molecule or molecules. ]]> This a bimolecular elementary reaction. A bimolecular elementary reaction is an elementary reaction in which two reactant molecules produce the product molecule or molecules. ]]> This is not an elementary reaction. Reactions involving more than two reactant molecules are not elementary. ElementRxnRateLaws01 Assume that the equation below represents an elementary reaction. Predict the rate expression (rate law) for this reaction.

CO(g) + Cl2(g) COCl2(g)

]]> 1 0.1 0 0 true false abc Rate = k[CO] You have included just one of the reactants. This is a bimolecular elementary reaction, so both reactants should be included in the rate law. 2]]]> You have included just one of the reactants. This is a bimolecular elementary reaction, so both reactants should be included in the rate law. 2 ][CoCl2]]]> You have included both products and reactants. To write a rate law for an elementary reaction, you only include the reactants. 2]]]> products. The rate law for this type of reaction has the general formula rate= k[A][B].]]> ExpDataRateConst01 Use the experimental data below to determine the rate constant for the following reaction.


]]> 1 0.1 0 0 true false abc 2/mol2·s]]> Correct! 2/mol2·s]]> You have the correct units, but you inverted the relationship. 2/mol2·s]]> You have the correct units but you forgot to square the concentration of B. Be careful of your units! You have the wrong units, and you inverted the relationship. You have the wrong units, and you forgot to square the concentration of B. FactorsAffectingRate01 Which of the following changes would NOT affect the rate of the reaction of cisplatin with water?
Pt(NH3)2Cl2(aq) + H2O(l) [Pt(NH3)2(H2O)Cl]+ + Cl-]]> 1 0.1 0 0 true false abc Using a 500 mL Erlenmeyer flask for the reaction instead of a 250 mL Erlenmeyer flask. Correct. The size of the container has no affect on the rate of reaction. Using 0.20 M cisplatin in the reaction instead of 0.10 M cisplatin. The rate of reaction is very much dependent on the concentration of the reactants. The rate of reaction is very much dependent on the temperature of the system. Adding a catalyst to the reaction system. The use of a catalyst will change the rate of reaction. InitialRateMethod01 Use the experimental data below to determine the rate equation for the following reaction.


]]> 1 0.1 0 0 true false abc Rate = k[A] A is first order and B is zero order. This is not the case here. The rate law must be determined by analyzing the effect of changing the concentration of reactants on the rate of reaction. What happened to the rate when the concentration of A was doubled (while the concentration of B was held constant)? What happened to the rate when the concentration of B was doubled (while the concentration of A was held constant)? Rate = k[B] A is zero order and B is first order. This is not the case here. The rate law must be determined by analyzing the effect of changing the concentration of reactants on the rate of reaction. What happened to the rate when the concentration of A was doubled (while the concentration of B was held constant)? What happened to the rate when the concentration of B was doubled (while the concentration of A was held constant)? Rate = k[A][B] Correct! A is first order and B is first order. The rate law must be determined by analyzing the effect of changing the concentration of reactants on the rate of reaction. What happened to the rate when the concentration of A was doubled (while the concentration of B was held constant)? What happened to the rate when the concentration of B was doubled (while the concentration of A was held constant)? 2[B]]]> A is second order and B is first order. This is not the case here. The rate law must be determined by analyzing the effect of changing the concentration of reactants on the rate of reaction. What happened to the rate when the concentration of A was doubled (while the concentration of B was held constant)? What happened to the rate when the concentration of B was doubled (while the concentration of A was held constant)? 2]]> A is first order and B is second order. This is not the case here. The rate law must be determined by analyzing the effect of changing the concentration of reactants on the rate of reaction. What happened to the rate when the concentration of A was doubled (while the concentration of B was held constant)? What happened to the rate when the concentration of B was doubled (while the concentration of A was held constant)? 2[B]2]]> A is second order and B is second order. This is not the case here. The rate law must be determined by analyzing the effect of changing the concentration of reactants on the rate of reaction. What happened to the rate when the concentration of A was doubled (while the concentration of B was held constant)? What happened to the rate when the concentration of B was doubled (while the concentration of A was held constant)? 2]]> A is second order and B is zero order. This is not the case here. The rate law must be determined by analyzing the effect of changing the concentration of reactants on the rate of reaction. What happened to the rate when the concentration of A was doubled (while the concentration of B was held constant)? What happened to the rate when the concentration of B was doubled (while the concentration of A was held constant)? 2]]> A is zero order and B is second order. This is not the case here. The rate law must be determined by analyzing the effect of changing the concentration of reactants on the rate of reaction. What happened to the rate when the concentration of A was doubled (while the concentration of B was held constant)? What happened to the rate when the concentration of B was doubled (while the concentration of A was held constant)? 2[B]3]]> A is second order and B is third order. This is not the case here. You cannot use the coefficients of the equation to determine the rate law. The rate law must be determined by analyzing the effect of changing the concentration of reactants on the rate of reaction. What happened to the rate when the concentration of A was doubled (while the concentration of B was held constant)? What happened to the rate when the concentration of B was doubled (while the concentration of A was held constant)? IntegratedRateLaw01 The following kinetics information may be useful in answering this problem.

Use the plots below to determine the order of the reaction with respect to A.



]]> 1 0.1 0 0 true false abc zero-order Correct. A zero-order reaction will result in a straight line when [A] is plotted vs time. first-order A first-order reaction will result in a straight line when ln[A] is plotted vs time. This is not the case here. second-order A second-order reaction will result in a straight line when 1/[A] is plotted vs time. This is not the case here. There is not enough information given to determine the order. The order of a reaction can be determined by collecting concentration/time data and then plotting [A], ln[A], and 1/[A] vs time. If one of the plots results in a straight line, then the order of reaction can be determined. IntermediateInMech01 Suppose that for the reaction of nitrogen dioxide and carbon monoxide
NO2 + CO NO + CO2

the following mechanism has been proposed at high temperatures:
(1) NO2 + CO O-N-O-C-O (slow)
(2) O-N-O-C-O NO + CO2 (fast)
Check the box for each species that is an intermediate in this mechanism.

]]> 1 0.1 0 0 false false abc 2]]> This is a reactant in the overall equation. Therefore, it cannot be an intermediate. O-N-O-C-O Correct! This is an intermediate. An intermediate is produced in one step of a mechanism and used up in a later step. It does not appear in the overall equation. NO This is a product in the overall equation. Therefore, it cannot be an intermediate. 2]]> This is a product in the overall equation. Therefore, it cannot be an intermediate. CO This is a reactant in the overall equation. Therefore, it cannot be an intermediate. None of the above is an intermediate. There is an intermediate in this mechanism. An intermediate is produced in one step of a mechanism and used up in a later step. It does not appear in the overall equation. RateLawChangeConc01 The rate law for a reaction is rate=k[A][B]. If the concentration of A doubles, the rate of the reaction will do which of the following?]]> 1 0.1 0 0 true false abc not change This would indicate the order of A is zero order. This is not the case here. increase by a factor of 2 Correct! The order of A is first order, which means the concentration of A is proportional to the rate of the reaction. increase by a factor of 4 This would indicate the order of A is second order. This is not the case here. increase by a factor of 8 This would indicate the order of A is third order. This is not the case here. RxnMechanisms01 Experiments show that the reaction of nitrogen dioxide and carbon monoxide
NO2 + CO NO + CO2

has the following rate expression at high temperatures:

Rate=k[NO2][CO]

Is the following mechanism compatible with the experimental information?
(1) NO2 + CO O-N-O-C-O (slow)
(2) O-N-O-C-O NO + CO2 (fast)
Choose the best answer.

]]> 1 0.1 0 0 true false abc Yes, the mechanism is compatible, because the mechanism sums to the overall reaction. The mechanism reactions do sum to the overall reaction, but this is not the only test for the compatibility of a mechanism. Yes, the mechanism is compatible, because the mechanism sums to the overall reaction and the mechanism predicts a rate law that agrees with the experimentally observed rate law. 2][CO].]]> Yes, the mechanism is compatible, because the mechanism predicts a rate law that agrees with the experimentally observed rate law. The mechanism does predict the experimental rate law, but this is not the only test for the compatibility of a mechanism. No, the mechanism is not compatible, because the mechanism does not sum to the overall reaction. does sum to the overall reaction. If you add the equations of the mechanism together, canceling each substance that is the same (including being in the same state) on both sides of the equation, they do sum to the overall equation given from the experiment.]]> No, the mechanism is not compatible, because the mechanism does not predict a rate law that agrees with the experimentally observed rate law. 2][CO]. This agrees with the experimentally observed rate law.]]> The compatibility of the mechanism cannot be determined from the information given. There is enough information to determine the compatibility of the mechanism. Compatibility is determined by comparing the mechanism to the experimental data. First, add the equations of the mechanism together and compare the overall equation to the experimental equation. Second, use the rate-determining step (the slowest step) of the mechanism to predict a rate law. Compare this rate law to the experimentally observed rate law. If both agree with the experimental data, then the mechanism is compatible. RxnProfileEaDeltaE01 Based on the reaction profile, what is the energy change for the reaction?
]]> 1 0.1 0 0 true false abc -17 kJ/mole E or H).]]> 50 kJ/mol This is the activation energy for the uncatalyzed reaction. 23 kJ/mol This is the energy of the products. 32 kJ/mol This is the activation energy of the catalyzed reaction.