Chemical kinetics Questions and Answers

10 ml of methyl acetate was taken in a flask containing 200 ml of 0 1 N HCI maintained at 30 C 20 ml o the reaction mixture was taken at different intervals of time and titrated with a standard alkali The following data were obtained Time minutes Alkali used ml The order of reaction is Zero order Second order 0 19 24 75 24 24 119 26 60 183 29 32 2 First order 4 Third order 80 42 03

4 7 For the reaction N O g 2NO g it has been found that the pressure of N O4 falls from 0 64 atm to 0 38 atm in 28 minutes Calculate the rate of reaction and the rate of appearance of NO g

4 For given reaction 2Bt aq A s 2B s A 2 If Keq of reaction is 1015 2 and E A 2 A 0 34V DA Then calculate E B B will be 1 0 80 loe onse 2 0 80 4 1 60 27

2 The rate constant for a first order reaction is 4 606 x 10 s 1 The time required to reduce 2 0 g of the reactant to 0 2 g is 1 100 s 1220 693 2 200 s 3 500 s 4 1000 s 1007 jo J 4606X1 103x2 4606 2x1 7

8 Kinetic data for hydrolysis of a 0 3 M solution of ethyl acetate in presence of HCI as catalyst is given in the following table A constant volume of reaction mixture is taken at different time and titrated against the same standard alkali solution at different time ime min 0 10 Vol of alkali solution ml 25 00 28 00 If the rate law is given as rate k Ester H where H is a catalyst find the rate in M min of ester hydrolysis in a solution which is 0 1 M each in ester ethyl ethyl acetate and acid 5 HCI In 2 4 0 225 A 4 5 10 4 C 4 5x10 6 t 40 00 B 4 5 10 5 D 4 5 10 7

09 An increase in the concentration of th reactants of a reaction leads to change in ten 1 1 len activation energy 2 heat of reaction 3 threshold energy 4 collision frequency

When 100 mL of IM HCl was mixed with 100 mL of 1 0 M NaOH in an isolated beaker at constant pressure a temperature increase of 5 7 C was measured for the beaker and its contents expt 1 Because the enthalpy of neutralisation of a strong acid with a strong base is constant 57 0 kJ mot this experiment could be used to measure the calorimeter constant In a second experiment Expt 2 100 mL of 2M acetic acid K 2 10 5 was mixed with 100 mL of 1M NaOH under identical condition to Expt 1 where a temperature rise of 5 6 C was measured Consider heat capacity of all solutions as 4 2 J gm K and density of all solutions as 1 gm mL Enthalpy of dissociation in kJ mot of acetic acid obtained in the Expt 2 is A 1 B 10 C 24 5 D 51 4

0 The time t 2 1 wha ase 3 times rd and win time period for and t are time completion of two first order reactions If the half lives are in the ratio 10 3 then the ratio of t and t will be 1 1 23 2 0 81 3 0 11 4 2 70

An increase in the concentration of the reactants of a reaction leads to change in activation energy heat of reaction 1 2 3 4 threshold energy collision frequency

De job wit Ecell 0 59 V at or the cell reaction V at T 298 K 17 149 If the rate constant for a first order reaction is k the time t required for the completion of 99 of the reaction is given by 1 t 0 693 k 69 2 d 1386 2 3 4 t 6 909 k t 4 606 k t 2 303 k is

On electrolysis of dil sulphuric acid using Platinum Pt electrode the product obtained at anode will be 1 Hydrogen gas Oxygen gas 3 4 H S gas SO gas Gigon 4 has 78 And

3 When weak acid is titrated with strong base then pH before after reaching end point respectively 1 pK pK pK salt acid 2 pK log PK 3 7 PK logc pk log salt 4 pK log cid a salt acid 1 7 pK logc

K K3 K b K K3 K A first order reaction has a specific reaction rate of 10 sec1 How much time will it take INEET 20 d 238 6 sec 20g of the reactant to reduce to 5g a 138 6 sec b 346 5 sec c 693 0 sec

5 For the following reactions write the rate of reaction expression in terms of reactants and products 2NO O i 4NH g 50 g 4NO g 6H O g ii 2N O 7 For the chemical decomposition of SO Cl its initial concentration is 0 8420 mol L and final concentration is 0 215 moll in 2 hours What is the average rate of this reaction

NE 24 A reaction having equal energies of activation for forward and reverse reactions has 1 AH AG AS 0 2 AS 0 3 AG 0 4 AH 0

38 The progress of the reaction AnB with time is presented in figure Determine the value of n i ii the equilibrium constant K iii the initial rate of conversion of A 0 5 0 3 0 1 1 3 CAREER INSTITUTE Path to Success KOTA RAJASTHAN 5 O 7 Time Hour

39 Listed in the table are forward and reverse rate constants for the reaction 2NO g N g O g Temperature K k M s 1400 1 1 x 10 6 1500 1 4 x 10 5 Is the reaction endothermic or exothermic Explain in terms of kinetics k M s 0 29 1 3

For a first order reaction rate constant is 1 x10 5 sec having E 1800 kJ mol Then value of InA at T 600K is 1 151 7 3 24 7 2 349 3 4 11 34

The acid catalysed hydrolysis of an organic compound A at 303 K has a time for half change of 100 minute when carried out in a buffer solution at pH 5 and 10 minute when carried out at 4 Both times of half change are independent of the initial concentration of A If the rate o pH reaction is given by K A H The value of y is d A dt

The rate constant of a first order reaction at 27 C is 10 min The temperature coefficient of this reaction is 2 What is the rate constant in min at 17 C for this reaction EAMCET 2006 a 10 3 c 2x10 5x104 d 10 2

Consider the reaction KCIO3 6 FeSO4 3H SO4 KCI 3Fe SO4 3 3H O If concentration of FeSO decreases from 0 9 M to 0 3 M in 10 second the rate of formation of KCI is in the above reaction would be In M sec

9 In the reversible reaction 2NO N O4 K rate of disappearance of NO is equal to 2 K 1 2K NO 1 K 27 2K NO 1 2K N O4 3 2K NO 1 K NO

Second order reactions Hydrolysis of ester by alkali Saponification CH COOC Hs NaOH CH COONa C H OH H 1 2HI 2HI H 1 2NO 2NO F NO 03 2CI O F 2NO O 2NO Fisio NO O 2Cl O For second order n 2 kt 1 1 1 2 1 a x a 1 a x 1 a

43 In following compressibility factor v s pressure graph which is true 8 N Z B C pressure Z 1 10 9 1 At high pressure gas B behaves as non ideal 2 At low pressure gas B behaves as ideal gas olioj pat to nomy 3 At low pressure gas A behaves as ideal gas 4 At low pressure gas C behaves as ideal gas

70 For the reaction 3A 2B C Products the following kinetic data was obtained Initial concentration A mol L B mol L C mol L 0 01 0 02 0 01 0 01 0 005 0 005 0 010 0 005 0 01 0 01 0 01 0 02 Initial rate mol L s 1 2 Rate k A B C 3 Rate k A B C 4 Rate k A B C 5 x 10 5 5 x 10 5 2 5 10 5 20 10 5 Hence the rate of reaction is given by 1 Rate k A B C

164 The enthalpies of formation of CO g and CO g at 298 K are in the ratio 2 56 1 For the reaction CO g C s 2CO g AH 177 5 kJ AH of CO g is 1 316 96 kJ mol 3 141 6 kJ mol 1 165 Which of the following properties has incorrect order 2 113 78 kJ mol 4 180 6 kJ mol

Which of the following does not affect the rate of reaction 1 Amount of the reactant taken 2 Physical state of the reactant 3 AH of reaction 4 Size of vessel

The fraction of total volume occupied by the cube is 4 382 382 Simple cube is 36 atoms present in a simple 1 R 6 2 TU 3 2 3 TU 4 2 4 4

26 Azo isopropane decomposes according to the equation CH3 2CHN NCH CH3 2 g N g C6H14 g It is found to be a first order reaction If initial pressure is Po and pressure of the mixture at time t is P then rate constant K would be 1 K 2 K 3 K K 2 303 t 2 303 t 2 303 t 2 303 log log log log Po 2Po Pt Po Pt Po 250 290 C Po Po P 2P

The pH of solution is increased from 3 to 6 Its H ion conc will be 1 Reduced to half 2 Doubled 3 Reduced by 1000 times 4 Increased by 1000 times YEXT

13 A reaction is 50 complete in 2 hours and 75 2013 in 4 hours The order of reaction i complete a 1 b 2 c 3 d 0 Karnataka NEET 201

285 The entropy of vaporization of benzene is 85 JK mol When 117 g benzene vaporizes at its normal boiling point the entropy change of surrounding is 1 85 J K Out 3 85 x 1 55 J K 2 85 x 1 5 J K 4 None of these

For a unimolecular if reaction AB has rate constant K another unimolecular reaction CD rate constant K If half life of first reaction is half of half life of second reaction then find Ea Ea will be 1 RT n2 2 RT n2 no 3 RT ln2 wolle 4 1 RTln2

s theory Idea of elliptical orbits In order to explain the fine structure of spectral lines in the hydrogen spectrum Sommerfeld in 1915 extended Bohr s heory and proposed that i An electron moves around a positively charged nucleus in different elliptical orbits in addition to circular orbits

51 For a first order reaction rate constant is given as log K 14 1 2x104 T 9 then what will be value of temperature if its half life period is 6 93 x 10 3 min 1 100 K 3 720 K 2 1000 K 4 327 K

Fig Average rate of V E 1 The decomposition of N O in CCl4 at 318K has been studied by monitoring the concentration of N O in the solution Initially the concentration of N O is 2 33 moll and after 184 minutes it is reduced to 2 08 moll The reaction takes place the equation according to 2N O g 4NO g 0 8 Calculate the average rate of this reaction in terms of minutes What is the rate of production of NO during the period Sol A N 0 At Rate 6 79x10 It may be understand that 1 A NO 4 At 1 Average 1 2 08 2 33 molL 1 2 molL min A NO A 184min rate 6 79 10 4 molL min 4x6 79x10 molL min

17 Select the law that corresponds to data shown for the following reaction 2A B C D Exp 1 2 3 4 1 Rate 3 Rate A 0 1 0 3 0 3 0 4 B 0 1 0 2 0 4 0 1 Initial rate 1 mol L min 7 5x10 9 0 10 3 6x10 3 0x10 1 K A B 2 K A B K A B 2 Rate 4 Rate K A B

What is the entropy change when 1 mole of a monoatomic ideal gas changes volume from 1L to 3L at constant temperature 3R 2 3 3R en 3 1 en3 5R 2 4 R en 3 2 en3

min 54 For a first order reaction t 0 A g B g C g a 10 77s 1 mol of SO Cl is denn a x If concentration of A is 0 1 M at 5 sec then from following graph the rate constant is 30 b 5 77 s b 3 47 x 10 d 1 73 x 10 5sec M min M min c 2 3s d 1 1

How much faster would a reaction proceed at 47 C than at 27 C if the activation energy of reaction is 65 kJmol 1 1 2 times 3 11 times 2 5 times 4 16 times

Graph of degree of dissociation a against t for reaction AB of different orders are as follows a I II 1 a The order of reaction 1 and II are respectively 1 0 1 2 1 2

For a reaction r k CH COCH3 3 2 the of reaction and rate constant respectively ar 11 1 mol L s mol 2 L2 s1 1 1 2 mol L s mol 2 L2s 1 1 3 mol L s mol 2 L2 s 1 1 4 mol Ls mol 2 L2s

If half life of a first order reaction is 2 min then the ratio of initial rate to the rate after two half lives is 1 3 IN NIT 2 2 1 2 4 4

A reaction is 50 completed in 4 hours and 75 in 6 hours The order of the reaction is completed 1 O 2 1 3 2 4 3

In the reaction A 2B CD 2E The rate of reaction remains unchanged if the conc of B is doubled and that of A and C is kept constant What is the order with respect to B 1 0 2 1 2 3 1 4 3

11 In a reaction 2HI H I the concentration of HI decreases from 0 5 mol L to 0 4 mol L in 10 minutes What is the rate of reaction during this interval 1 a 5 x 10 3 M min 1 c 5 x 10 2 M min 3 1 b 2 5 x 10 M min d 2 5 x 102 M min

103 A chemical reaction was carried out at 300 K and 290 K If the rate constants of the reactions are k and k respectively then a k k c k 0 125 k b k 2k d k 0 5 k

The half life of a first order reaction is 30 min The time required for 75 completion of the same reaction will be A 45 min 30 13 75 off B 60 min C 75 min D 90 min

Find exothermic reaction 1 F F e 2 F Cl F Cl 3 Xe He Xe He 4 O 2e00

84 Consider two reactions 1 and 2 having energies E and activation E respectively When the temperature is changed from 400 to 450 K the rate constant for the first reaction changes from k to kand that for the second reaction changes from k to k If E E then which of the following expressions is true for the reactions a K K K K b K K 1 k