Chemical kinetics Questions and Answers

For a gaseous phase reaction 2A g 3B g Pressur A changes from 2 atm to 1 5 atm in 10 seconds T 30 Calculate i Rate of reaction in atm sec M sec 1 ii Pressure of B in the same time interval

Energy of activation of forward reaction for an endothermic process is 50 kJ If enthalpy change for forward reaction is 20 kJ then enthalpy change for backward reaction will be AIIMS 2013 D 50 kJ A 30 kJ B 20 kJ C 70 kJ

Pure ozone decomposes slowly to oxygen 203 g 30 g Three plots were made below Using this date determine the form of the rate law In 03 M 1 03 1 M Time h 03 M 0 2000 7600 10000 12300 14300 101 M 17000 LIKW LAVE ARK 6 ADR AS XV 26108 4 FHOIL a rate K 0 1 Ob rate c rate k 000000000 1 1031 1 00E 03 4 98E 06 2 07E 05 1 66E 05 d rate k 20 1 39E 05 1 22E 06 1 05E 06 WEN 1 20 06 1000 06 ECCE CS 400 DS 4 00K 15 200405 100 0 0 3000 113 33000 URE IN 12 2 13 1 13 3 13 3 136 13 8 50 215100115 941 15000 borw 1 00E 05 2 01E 05 4 83E 05 6 02E 05 7 19E 05 8 20E 05 9 52E 05 The 001234 SOLON 1000

The half life for the decay of radium is 1620 years What is the rate constant for this first order process O 6 17 x 104 yr 1 O 8 91 x 104 yr 1 O 2 33 x 104 yr 4 28 x 10 4 yr 1 1 12 x 104 yr

5 Technetium 99m is used as a radioactive tracer for certain medical tests It has a half life of 1 day Consider the d is the amount of radioactive material remaining d days after the test Write a log expression that represents the number of days until only 7 amounts of radioactive material remains 1 function T where T d 800

Give In neutral solution k 2 1x 10 11 s 1 at 27 C and 5 8 x 10 11 s 1 at 35 2 C Determine the activation energy of this reaction in kJ EA In k k 1 R T T must be in Kelvin where R 8 314 J mol K hint Temperature Report your answer to 1 decimal place Your Answer

Which of these K values indicate that the forward reaction is favored O K 1 OK 0 5 OK 4 3 x 104 OK 1 2 x 10

At 514 Kelvin a first order reaction has a half life of 9 48 s The same reaction has a half life of 175 s at 366 Kelvin Calculate the activation energy kJ mol for the reaction Enter your answer to 1 decimal place 24 3

mechanism A reaction has the following proposed mechanism A2 g B s A B s fast A B s A g AB s slow AB s C g AC g B s fast A g C g AC g fast Mrchanism tops 1 4 points The species B is properly described as a heterogeneous catalyst a homogeneous catalyst an intermediate an activated complex a product of the overall reaction 2 00000 4 points Which species are intermediates Select all that apply Incorrect choices will be penalized C 0000000 DO A B AB A A AC B 1 Kale Kfl21 Rate k 0

Mrchanism Suppose a reaction occurs with the following mechanism All are elementary steps kf Step 1 O g 20 g fast Step 2 Step 3 O g N g K NO g ky O g N g 2 NO g N g slow very fast 5 4 points What is the rate law for the rate determining step Rate k 0 Rate k O N 000000 Rate f21 Rate k 0 12 Rate k 0 6 Rate k 0 12 Rate k 0 k 0 Rate k 0 Rate k O N 5 points What is the overall rate law for this reaction Rate K N 0 1 2 Rate kr 0 k 0 Rate K N 0 2 Rate k 0 1 Rate k O N 2 OOOOC

Potential energy diagram Potential energy D A B E Reaction coordinate C 01 24 05 Time Remaining 22 3 points Which letter represents the transition state activated complex A 00000 00000 E 24 C B 23 4 points Which letter represents the activation energy D D A B E C 4 points Which letter represents the enthalpy E D Subm

4 points Which of the following factors have effect on the rate of a chemical reaction Select all that apply Incorrect choices will be penalized the standard enthalpy of reaction for the system activation energy a catalyst the concentration of the reactants the temperature

Arrhenius plot Experimental data was plotted to obtain the following Arrhenius Plot In k 1 T K 16 5 points If Arrhenius Plot has the equation y 5 517 x 104 xX 45 7 calculate the activation energy in kJ mol of the reaction Do not write unit in answer Report your answer with one place past the decimal point Type your answer

1 4 points Select the reactions below that are elementary reactions as written Select all that apply Incorrect choices will be penalized 2 NO2 g NO3 g NO g Rate K NO 2 Rate k NO Rate k NO 0 Rate K NO 2 H 1 0000 NO2 g CO g CO2 g NO g 2 NO g O2 g 2 NO2 g 2 NO g 2 H2 g N2 g 2 H O g

ICE Chart Consider the following reaction and complete the ICE chart using given data N O4 9 2 NO2 9 N O4 9 2 NO g Reaction Initial Change Equilibrium 18 19 4 points A student placed 0 550 mol of N O4 g into a 2 2 L container at 23 5 C At equilibrium it was found that the flask contained 0 210 mol of NO g What is the Ke for this reaction Keep the answer with 3 decimal places Type your answer 4 points A student placed 0 590 mol of N2O4 9 into a 1 8 L container at 24 4 C At equilibrium it was found that the flask contained 0 226 mol of NO g What is the change in concentration M of N O4 g Do not write unit in the answer and keep the answer with 3 decimal places Incorrect sign won t receive credits Tynoy

The activation energy for a particular reaction is 102 kJ mol If the rate constant is 1 35 x 10 s at 308 K what is the rate constant at 273 K

Use the following data to determine the rate law for the chemical reaction 2 NO g Br g 2 NOBr g Round your orders to the nearest tenths place Provide the correct value of the rate constant k with units 1 2 3 Trial Initial Rates Data for Given Reaction NO M Br M 0 10 0 25 0 10 0 20 0 20 0 50 Initial Rate M s 37 5 150 60

Multiplying and collecting terms yield the quadratic equation where a 4 b 0 45 and c 0 630 4x 0 45 0 630 0 From the quadratic formula the correct value for is x 0 34 atm The equilibrium pressures can now be calculated from the expressions involving PNO 2 0 34 atm 0 69 atm PN 04 1 4 atm 0 34 atm 1 1 atm bA flask containing only NO at an initial pressure of 2 8 atm is allowed to reach equilibrium Calculate the equilibrium partial pressures of the gas Enter your answer to two significant figures Partial pressure of NO Partial pressure of N O4 atm atm

Write the rate laws for the following elementary reactio Use k for the rate constant a CH3 NC g CH3 CN 9 Rate b 03 g NO g O g NO2 g Rate c 03 g O2 g O g Rate d 03 g 0 g 202 g Rate

Consider two reactions one that is second order and one that is third order Which best describes the effect on the reaction rates by INCREASING the concentration of all reactants OOOO The rate increases for only the second order reaction The rates decrease for both reactions The rates increase for both reactions The rate decreases for only the third order reaction

te the rate laws for the following elementary reaction se k for the rate constant a CH3 NC g CH3 CN g Rate b O3 g NO g O g NO2 g Rate c 03 g O2 g 0 g Rate d O3 g 0 g 202 g Rate

At 40 C H O aq will decompose according to the following reaction 2H O aq 2H O l O g The following data were collected for the concentration of H O2 at various times Time s H O2 mol L 0 1 33 x 104 2 66 x 104 1 900 1 240 0 809 a Calculate the average rate of decomposition of H O2 between 0 and 1 33 x 104 s Average rate mol L s Use this rate to calculate the average rate of production of O g over the same time per Average rate mol L s b What are these rates for the time period 1 33 x 104 s to 2 66 x 10 s mol L s Rate of H O2 decomposition Rate of O2 production mol L s

The reaction 2 NO g O g 2 NO2 g was studied and the following data were obtained where Rate A 0 At NO o molecules cm 1 00 10 8 3 00 1018 2 50 10 8 02 0 molecules cm 1 00 10 8 1 00 1018 2 50 10 8 Initial Rate molecules cm s 2 00 x 10 6 1 80 10 7 3 13 1017 What would be the initial rate for an experiment where NO 1 86 x 10 8 molecules cm and 0 8 37 10 8 molecul Rate molecules cm s

bA flask containing only NO at an initial pressure of 4 2 atm is allowed to reach equilibrium Calculate the equilibrium partial pressures of the gase Enter your answer to two significant figures Partial pressure of NO2 Partial pressure of N204 atm atm

The reaction NHASH s NH3 g H S 9 has Kp 0 10 at 27 C What is the minimum amount of NH4SH that must be present for this reaction to be at equilibrium in a 10 0 L co g

The activation energy for the reaction H2 g I2 g 2 HI g is 165 kJ mol and AE for the reaction is 25 kJ mol What is the activation energy for the decomposition ER kJ mol

The decomposition of nitrosyl chloride was studied 2NOCI g 2NO g Cl 9 The following data were obtained where A NOCI At Rate NOCI molecules cm molecules cm s 3 0 1016 3 56 104 2 0 10 6 1 58 x 104 1 0 10 6 3 95 10 4 0 10 6 6 32 104 a What is the rate law Use k for the rate constant Rate Initial rate b Calculate the value of the rate constant cm molecules s c Calculate the value of the rate constant when concentrations are given in m k

A reaction is run and the rate constant measured over a range of temperatures The results are listed below Calculate the value of E for this reac T K k L mol s 3 27x10 2 293 303 0 130 313 0 474 323 333 1 60 5 00 HOW DO WE GET THERE The plot of In k vs 1 T is shown here The slope of the line is 1 23x104 K mol Use that to calculate the activation energy In k 0 0029 0 003 0 0031 0 0032 0 0033 0 0034 1 T K 1 0 0035 0 0036 W

The reaction 2 NO g Br 9 2 NOBr g has Kp 109 at 25 C If the equilibrium partial pressure of Br2 is 0 0138 atm and the equilibrium partial pressure of NOBr is 0 0583 atm calculate the partial pressure of NO at equilibrium Partial pressure atm

A certain first order reaction is 28 complete in 35 s What are the values of the rate constant and the half life for this process k t1 2 1

The isomerization of methyisocyanide CH3NC to acetonitrile CH3CN is a first order reaction If 2 56 mg of CH3NC is present initially and 1 89 mg is present af 474 min at 230 C what is the value of the rate constant k Assume the volume is constant X min 1

Ethyl ethanoate commonly called ethyl acetate CH3CO C H5 is an important solvent used in nail polish remover lacquers adhesives the manufacture of plastics and even as a food favoring It is produced from acetic acid and ethanol by the reaction CH3CO H C H5OH CH3CO C H5 H O ethanoic acid acetic acid ethanol ethyl ethanoate ethyl acetate At 25 C Kc 4 10 for this reaction In a reaction mixture the following equilibrium concentrations were observed CH3CO H 0 317 M H O 0 00753 M and CH3CO C H5 0 747 M What was the concentration of C H5OH in the mixture Fill in the Blank Question 41 Fill in the Blank Question 4 Numeric Fill in Question Multipart Question Multiple Sele Question Multipart Questic Numeric P

Choose the best answer Plot the curve of product or reactant amounts as a function of time and draw a tangent line at the time tof interest O Divide the total concentration of all products by the exact time when the reaction is completed Plot the curve of product or reactant concentrations as a function of time and draw a tangent line at the time of interest O Divide the concentration of one of the products by the exact time when the reaction is completed X Incorrect What data do you need to determine the instantaneous rate of the reaction The concentration of a reactant or the concentration of a product as a function of time The amounts of a reactant or the amounts of a product as a function of time The amounts of all reactants and the amounts of all products as a function of time the concentrations of all products as a function of time

numpin Rate constants were measured at various temperatures for the reaction HI g CH31 g CH4 g 12 g The following data were obtained Rate Constant L mol s 1 91 x 10 2 74 x 10 3 90 x 10 5 51x10 7 73 x 10 and 1 08 x 10 1 Temperature C 2 05 x 10 2 10 x 10 2 15 x 10 2 20 x 10 2 25 x 10 2 30 x 10 Determine the activation energy in kJ mol both graphically and by calculation using the equations In k In A E R 1 T In 2 Ea R For the calculation of Ea use the first and last sets of data in the table above Graphical determination of E i kJ mol

What is a homogeneous catalyst How does it function in general terms Select all that apply A homogeneous catalyst is present in the same phase as the reactants A homogeneous catalyst is present in a different phase than the reactants A homogeneous catalyst is used in one step but then regenerated in another O A homogeneous catalyst appears in the net overall equation for the reaction

The rates of many reactions approximately double for each 10 C rise in temperature Assuming a starting temperature of 29 C what would the activation energy be in kJ mol if the rate of a reaction were to be twice as large at 39 C kJ mol 1

What two factors influence the effectiveness of molecular collisions in producing chemical change The concentration of the reactants The kinetic energy of the reactants in relation to the activation energy The pressure The orientation of the remants

Describe how to determine the instantaneous rate of chemical change Choose the best answer Plot the curve of product or reactant amounts as a function of time and draw a tangent line at the time tof interest Divide the total concentration of all products by the exact time when the reaction is completed Plot the curve of product or reactant concentrations as a function of time and draw a tangent line at the time of interest O Divide the concentration of one of the products by the exact time when the reaction is completed X Incorrect What data do you need to determine the instantaneous rate of the reaction The concentration of a reactant or the concentration of a product as a function of time The amounts of a reactant or the amounts of a product as a function of time The amounts of all reactants and the amounts of all products as a function of time The concentrations of all reactants and the concentrations of all products as a function of time

Estimate the rate of the reaction H aq OH aq H O l given that the rate law for the reaction is rate 1 3 x 10 1 L mol s OH H and H 1 0 x 107 M and OH 1 0 x 107 M Express your answer in units of mol L s rate molls 1

Hydrogen sulfide burns in oxygen to form sulfur dioxide and water If sulfur dioxide is being formed at a rate of 0 319741078131 mol L s what are the rates of disappearance of hydrogen sulfide and oxygen Rate of disappearance of O2 is i mol L 5 mol L s Rate of disappearance of H S is i

Carbon 14 has a half life of 5720 years and this is a first order reaction If a piece of wood has converted 75 of the carbon 14 then how old is it 1430 years 4750 years O 2375 years 11440 years 4290 years

Given the following proposed mechanism predict the rate law for the overall reaction 2 NO2 Cl 2 NO Cl overall reaction Mechanism NO2 Cl2 NO CI CI slow NO2 CI NO Cl fast O Rate k NO CI Rate k NO CI CI k NO C1 Rate k NO Cl2 Rate Rate k NO CI CI

According to the mechanism below what is the rate of production of C6H5 2CHI C6H5 2CHNO2 C6H5 CH NO C6H5 CH C6H5 2CHI Hint Use the steady state approximation to obtain an expression that depends on the concentrations of reactants or products only with no reaction intermediates Rate Rate Rate Rate Rate K 1 k k1k2 k 1 C6H5 2CHI NO C6H5 2CHNO 1 C6H5 2CHNO2 I k1k2 C6H5 2CHNO 1 k NO k2 1 k1k2 k 1 Rate k1 k 1 k2 C6H5 2CHNO I k1 C6H5 2CHNO I k 1 k1k2 C6H5 2CHNO2 I k I k2 NO

A rate is equal to 0 0200 M s If A 0 100 M and rate k A what is the new rate if the concentration of A is increased to 0 200 M O 0 0400 M s 0 0600 M s 0 0800 M s 0 100 M s 0 0200 M s

A reaction is followed and found to have a rate constant of 3 36 x 10 M s at 344 K and a rate constant of 7 69 M at 219 K Determine the activation energy for this reaction 12 5 kJ mol 23 8 kJ mol 42 0 kJ mol O 58 2 kJ mol O 11 5 kJ mol

The first order decomposition of cyclopropane has a rate constant of 6 7 x 10 4 s If the initial concentration of cyclopropane is 1 33 M what is the concentration of cyclopropane after 644 s 0 43 M 0 67 M 0 15 M 0 94 M 0 86 M

Determine the rate law and the value of k for the following reaction using the data provided S O8 aq 31 aq 2 SO4 g 13 aq Trial 1 2 3 S 08 M 0 30 0 44 0 44 O Rate 23 M 1 2 1 S 08 2 O Rate 86 M 5 S 08 11 O Rate 36 M s S 08 1 O Rate 195 M s S 08 1 1 1 Rate 120 M s S 08 1 1 1 i M 0 42 0 42 0 21 Initial Rate M s 4 54 6 65 3 33

Write a balanced reaction for which the following rate relationships are true Rate 1 2 A N205 1 A NO At 4 At 2 N O5NO2 402 ONO 0 N O5 4 NO2 O2 2 N O5 ON 05 NO O O2 N O5 4 NO O 4 02 At

The half life for the second order decomposition of HI is 15 4 s when the initial concentration of HI is 0 67 M What is the rate constant for this reaction O 9 7 x 10 2 M 5 3 8 x 102 M 51 O 1 0 102 M 5 O 2 2 102 M 5 4 5 x 102 M s1

For the gas phase decomposition of hydrogen peroxide at 400 C 2 H2O22 H2O 02 the average rate of disappearance of H2O2 over the time period from t 0 s to t 49 s is found to be 4 16x10 4 M s 1 The average rate of formation of O2 over the same time period is M s 1