Chemical kinetics Questions and Answers

min 1 4 4 6 x 10 min 53 The activation energy of a certain reaction is 50 kJ mol 1 in the absence of catalyst at 27 In the presence of catalyst the activation energy becomes 20 kJ mol 1 at the same temperature The temperature at which rate of uncatalysed reaction becomes equal to the rate in presence of catalyst at 27 C is Assume Arrhenius parameter A remains constant 1 500 K 3 250 K 2 750 K 4 1000 K

same for first second and third order reactions Which one is true at a definite moment for rate of these three reactions if concentration of reactants is same and less than 1 M Question Type Single Correct Type 1 2 3 r r2 13 r1 r2 r3 r r2 r3 None of these

1 In addition to performing the reaction N N 2 NH3 nitrogenase is also capable of catalyzing the following reactions Propose a catalytic cycle mechanism starting from intermediate E4in the previous pages for this reaction N N N N2 NH3

he half life period of a gaseous substance undergoing thermal decomposition was measured for various nitial pressure P with the following results mm 6300 5250 1 2 min 136 112 5 Calculate the order of the reaction

A product follows the mechanism as A A A A A A A A Akproduct Choose the correct statements The reaction is 2nd order at low concentration of A vori The reaction is 1st order at higher concentration of C The reaction is zero order D The reaction is 1st order at low concentration of A

In the reaction the number of molecules colliding with sufficient energy be unity for a reaction taking place at 500 K Then the activation energy Ea of the reaction is Ea 0 O Ea 1 O Ea 1 O Ea 1

2 57 Graph between log x m and log p is straight line inclined at an angle of 45 When pressure is 0 5 atm and 1k 0 693 the amount of solute adsorbed per gm of adsorbent will be

4 5 27 79 The increase in rate constant when its temperature is raised from 300 K to 320 K if activation energy for the reaction is 10 kcal mole is 2 81 8 8 58 1 100 3 183 3

Q 59 The following sequence of reaction occurs in commercial production of aqueous nitric acid 4NH3 g 5O g 4NO g 6H O l AH 904 kJ 1 2NO g O g 2NO g BAD HOOD DH 1 AH 1124 kJ 2 HOO 3NO g H O 1 2HNO3 aq NO g D you AH 140 kJ 3 banka The total heat liberated in kJ at constant pressure for the production of exactly 1 mole of aqueous nitric acid by this

WORKED OUT EXAMPLES EXAMPLE 14 1g of graphite is burnt in a bomb calorimeter in excess of oxygen at 298 K and I am pressure accom to the equation Cigr Ogg CO g During the reaction temperature rises from 298 K to 299 K If the heat capacity of bomb calorimeter is 20 7 kJ K N C E R T 20 K

2 51 Given that the temperature coefficient for the saponification of ethyl acetate by NaOH is 1 75 The activation energy for the saponifiocation of ethyl acetate is K cal mol

Half life for the zero order reaction A g X g B g C g and half life for the first order reaction Y g are equal If completions time for the zero order reaction is 13 86 min then calculate the rate constant in hr for the reaction X g Y g

by 2 The Activation energy is lowered 8 314 kJ mol for the catalysed reaction The ratio of the rate of the catalysed reaction to that of the uncatalysed reaction at 500K is Given e 7 38 1 7 38 2 14 5 3 8 37 4 4 83

71 For two first order chemical reactions A Products B Products A and B are present initially as A 8 Bo and t 2 of A 10 min t2 of B 20 min If they start reacting at the same time then after how much time in minutes concentration of both would be same

52 For a reaction with rate equation kC Co dt and C are the concentration at time t 0 and T respectively If 10 min are required for C to Co 2 become the time in minutes required for Co 30 to become 4 is n

5 TEMPERATURE DEPENDENCE OF RATE ACTIVATION ENERGY In gaseous reactions important for understanding the upper atmosphere H O and O react bimolecularly to form two OH radicals AH for this reaction is 72 kJ at 500 K and E 77 kJ mol then calculate E for the bimolecular recombination of 20H radicals to form H O O at 500 K a

75 The dissociation of Nitrogen pentoxide is a first order reaction In first 24 min 75 of N O is dissociated The percentage of NO left behind after one hour of the start of reaction is approximately

Question No 4 40 Which of the following is the curve for Fermi Dirac statistics 4698 f K 200 0 5 X Y 2006469 AO None BOX NX 54696 202 26 2020064 2020 020064696 2 20064696 696 2020064 064696 202

In which reaction taking place at constant temperature the system does work on the surroundings II NH Cl s 1 Ag aq Cl aq AgCl s III 2NH3 g N g 3H g a I b III c II a III T NH g HCl g d 1 and

t 0 ta A gaseous reactant X decompose to produce gaseous product B C in a parallel reaction both by first order as follows K1 3 A A a a n KLC X g k 2 x 10 min B g k 3 x 10 min C g B B 1 KI k K Iw kitk Alt A o kit t If the decomposition is carried out in a sealed flask partial pressure of B after very long time was found to be 100 mm Hg Determine the time when pressure of X g was 100 mm Hg In2 0 693 A deum for the tv

Calculate the initial reaction rates for Experiments elapsed times Use correct units Laboratory temperature 23 8 C Experiment Trial 2 Start ddddddo End 2 20 2 43 1 16 1810 1805 1 15 1 35 Elapsed Time s 130 150 76 ave 140 70 65 75 95 Temp 34 8c ave 73 ave 70

The rate of a second order reaction 2A products is 8 x 10 4 mol L 1 s1 when concentration of A is 2 mol L 1 The rate constant of the reaction is A C 4 x 10 L mol s 8 x 10 L mol s 1 x 10 L mol s 2 10 L mol s

69 For a generalized nth order reaction AP the incorrect deduction is 1 1 A kt n 1 A DAT A concentration of A and k is rate constant B The expression of half life is t where A and A are initial and has instantaneous 1 21 1 k n 1 A C If n 0 concentration of A decreases linearly with time D If n 1kt 9

Jestion No 20 40 A reaction proceed through the formation of an interme unimolecular reaction A kaB kb C The integrated rate law for this reaction is AO A A e kart A BO A 14 2 co A A 1 c ka c kb 9691 200646 646 1 k kb k kb 4696 20 V A e k e kb 2020064696 202006 0064696 2020 202 9 4696 20200

64 Which of the following plot do not represent first order reaction R initial concentration of reactant R concentration of reactant at time t A C log R rate Slope time B 2 303 B D luz log R log R Conc

Question No 6 40 H and Br react to give HBr by the following steps Br M 2Br M fast 064696 2020064696 20064696 202006 96 23 2006 4696 202 Br H 2HBr H slow H Br HBr Br fast The probable rate law for the above sequence is AO Rate k k H Br BO Rate k ky H Br CO Rate k K H Br Rate k H B 696 4696 2020064 020064 2020 969

2 Which of the following statement is not wrong A In a chemicial reaction slow step is not rate determining step B Inversion of cane sugar is first order reaction C In Arrhenius equation plot of Ink vs 1 T is straight line D In first order reaction half life period is dependent of initial concentration 1

57 For the reaction A B Products The initial concentrations of A and B and the initial rate are mentioned below A B 5 0 20 0 30 5 07x10 5 0 20 0 10 5 07x10 5 0 40 0 05 1 43x 10 4 The orders with respect to A and B respectively are A Zero and one B One and zero C 1 5 and zero D Zero and 1 5

The decomposition of N O according to the equation 2 N O g first order reaction After 30 min from start of decomposition in a closed vessel the total pressure developed is found to be 284 5 mm Hg On complete decomposition the total pressure is584 5 mm Hg Calculate the rate constant of the reaction onctant for disappearance of A is 7 48 x 10 3 sec Calculate the f 1 atm to rise to

B The reaction A proceeds in parallel channels A Suppose the half life values for the tw C branches are 60 minutes and 90 minutes what is the overall half life value

In a gaseous reaction A 3B AB g the initial rates are as follows A 0 1 M 0 2 M 0 3 M 0 4 M B 0 1 M 0 1 M 0 2 M 0 3 M The rate law is Rate 0 002 mol L 0 002 mol L s7 0 008 mol L 1 0 018 mol LS

A certain zero order reaction has K 0 024 Ms1 for the disappearance of A What will be the concentration of A after 15 seconds if the initial concentration is 0 50 M A B D 0 50 M 0 375 M 0 14 M 0 060 M

Determine the order of reaction its rate The half life period of decomposition of a compound is 50 minutes If the initial concentration is halved the half life period is reduced to 25 minutes What is the order of reaction OF BATE CONSTANT USING DIFFERENT PARAMETERS

1805 Question No 3 40 In 20a consecutive first order reaction 46989 20200646 A B2C Where k and k are respective rate constant species B has transien existence therefore AO K k BOK 2k cok k DO K K 2020064696 21 0064696 202006 1696 2020064696 6 201

2 experimental method to calculate order and rate law of eaction and methods to monitor the progress of reaction 26 Formation of NO F from NO and F as per the reaction 2NO g F g 2NO F g is a second order reaction first order with respect to NO and first order with respect to F If NO and F are present in a closed vessel in ratio 2 1 maintained at a constant temperature with an initial total pressure of 3 atm what will be the total pressure in the vessel after the reaction is complete 1 latm 3 2 5 atm 2 2 atm 4 3 atm

ostion No 32 40 The mechanism of the decomposition of ethane is given as C H2CH CH C H6 CH4 C H C H C H4 H H C H6 H C H H C H C H6 For which of the following species steady state approximation can be app AO C H BOC H6 COC H CHA

2 53 For a reaction Ag nB the rate constant is 6 93 x 10 sec The reaction is performed at 8 constantpressure and temperature of24 63 atm and 300 K starting with 1 mole of pure A 3 M 3 25 H If concentration of B after 2000 sec is then the value of n is

0 001x107 A certain substance A is mixed with an equimolar quantity of substance B At the end of an hour A is 75 reacted Calculate the time when A is 10 unreacted Given order of reaction is zero A B 75x t anirs 17 1

The rate law for the reaction 0 00181 2 NO g Cl2 g 2 NOCI g is given by the goo rate K NO Cl The reaction occurs in the followi steps to per NOC12 g NOC12 g NO g 2NOCI g Identify the rate determining step 1 NO g Cl2 g ii

3 The rate constant of a reaction is 1 5 107 s 1 at 50 C and 4 5 x 107 s 1 at 100 C What is the value of activation energy 1 2 2 103 J mol 1 3 2 2 104 J mol 1 2 2300 J mol 1 4 220 J mol 1

3 The resistance of a KCI aqueous solution is 10 Xx24592 If the electrodes in the cell are 4 cm apa and area having 7 cm2 each the mola conductance of the solution will be 1 233 3 23 32 2 2 33 4 0 233

Q73 Select the correct statement out of I II and III for zeroth order reaction I Quantity of the product formed is directly proportional to time II Larger the initial concentration of the reactant greater the half life period III If 50 reaction takes place in 100 minutes 75 reaction take place in 150 minutes doubt ang speed I only Band II only C II and III only D I II and III only Q 74 Identify the strongest base Q 73 an is Axy 2 K 1 V 300 2XV 7 Q 74 W T II aftame at fre gargara 3 50 III 100 Peso fam 1150 2 affe 1 A B 1 II C S4 II I D 1 II NH III

Q 73 Select the correct statement out of I II and III for zeroth order reaction I Quantity of the product formed is directly proportional to time II Larger the initial concentration of the reactant greater the half life period III If 50 reaction takes place in 100 minutes 75 reaction take place in 150 minutes doubt CA Igaly Band II only C II and III only D I II and III only ang sheed F V Q74 Identify the strongest base 2Y NH 2 300 Q 73 fer IK 1 II VE3ee 2 7 III 100 2 50 fa R 150 C 31 A S 1 B I C II D 1 II NH 74 1 II III III

6 Co NH3 6 3 6 4 A first order reaction has a specific reaction rate of 10 2 sec 1 How much time will it take f 20 g of the reactant to reduce to 5g log 4 0 6020 1 138 6 sec 2 346 5 sec 3 693 0 sec 4 238 6 sec

List I List II A AG 0 I K 1 B AG 0 II K 1 C AGO 0 III K 1 Choose the correct answer from the options given belov 1 A I B II C III 2 A II B I C III 3 A I B III C II 4 A II B III C I

The rate constant for the decomposition of ethyl chloride is 4 12 10 5 s 1 at 22 3 C If the reaction s activation energy of 249 kJ mol at what temperature will its rate constant be 5 84x10 4 S 1 Answer in celsius

of Steady State An assumption Approximation is 1 polr Reaction occurs without the formation of intermediates One of the intermediates in the reaction is consumed as quickly as it is generated Equilibrium state is attained at the end of a reaction Catalyst does not accelerate reaction rate

The resistances of CH3COOCI3 solutions of various concentrations measured at 25 C using a conductivity cell with a cell constant of 0 2063 cm 1 are given as follows C mol L 0 0005 0 001 R ohm 3314 1669 a limit molar conductivity b dissociation constant 0 005 342 1 0 010 174 1 0 020 89 08 0 050 37 14

The most convenient method to protect the botto of ship made of iron is 1 Coating it with red lead oxide 2 White tin plating 3 Connecting it with Mg block 4 Connecting it with Pb block

The decomposition of gas at an initial pressure of 600mm of Hg was studied in a close vessel at a certain temperature The gas was found to be 50 decomposed in 30 minutes and 75 decomposed in 90 minutes Show that the reaction is of second orde and calculate the rate constant 3 marks