Chemical kinetics Questions and Answers

2 Calculate the rate constant for decomposition of ammonium nitrite from the following data NH4NO N 2H O Time minutes Vol of N ml 10 6 25 25 13 65 Given that the reaction follows first order kinetics 1 0 0197 min 1 3 0 197 min 1 2 4 35 05 1 97 min 1 None of these

Should option 2 be 3rd order 4 0 1 1 9 In which of the following option the example and the given order is incorrectly matched 1 H O H O 0 1st order 02 1st order 2 2NO Cl 2NOCI 2nd order 3 CH3COOCH3 NaOH CH3COONa CH3OH 2nd order 4 HI g Au H g 1 g Zero order

7 A first order reaction is found to have a rate constant k 7 39 105 S this reaction For first order reaction 2 k H 2 303 t a For t 2 X 2 2 303 k log log 2 303 k a a log2 a x 9 38 x 10 s a 2 2 303x0 3010 7 39x10 5 und 1 2 0 693 Find the half life of S 7 39x10 9 37 x 10 1 Read Office Aakash Tower 8 Pusa Road New Delhi 110005 Ph 011 47622456 9 37x10 7 My answer doesn t comes out to be the same and comes 7 37x10 5 Can t we apply formula for half life directly as t1 2 0 693

10 ml of 0 1 M of an acid was added to 50 ml The following reading of 0 1 M Na S2O3 were obtained lnk T in K 4 250K 5 333 33 K 6 500 K 7 1000 K K is the rate constant in s 1 Find activation energy in kcal mole R 2 cal mol K 1

t the point of intersection of the two curves shown the concentration of B is given by Conc A A nA0 2 B Ao n 1 Time nA0 n 1 Correct Answer B 9 for the first reaction A nB

10 ml of 0 1 M of an acid was added to 50 ml of 0 1 M Na2S2O3 The following readings were obtained InK T in K 4 250K 5 333 33 K 6 500 K 7 1000 K K is the rate constant in s 1 Find activation energy in kcal mole R 2 cal mol K 1 1000 2

One of the most harmful isotopes released in a nuclear accident is Cs 137 Its half life is 30 years and follows first order decomposition If the initial activity of isotope at site is 100 times its safe level how many years will it take for the site to be safe log2 0 3

a culture of bacteria a sample is taken at 10 00 AM and contains 1000 cells per ml A second sample at 8 00 PM has 10 000 cells per ml What is the generati me time required for number of bacterial cells to double in hours assuming first order overall growth log2 0 301

SECTION 1 NUMERICAL ANSWER BASED QUESTIONS A hydrogen like atom atomic number Z is in a higher excited state of quantum number n This excited atom can make a transition to the first excited state by successively emitting two photons of energies 10 20 eV and 17 00 eV respectively Alternatively the atom from the same excited state can make a transition to the second excited state by successively emitting two photons of energy 4 25 eV and 5 95 eV re 13 6 eV spectively Determine the value of n z ionisation energy of hydrogen atom 1

What volume of CO at STP is required to reduce one mole of Fe2O3 in the following reaction Fe2O3 CO Fe CO 11200 cm

10 ml of 0 1 M of an acid was added to 50 ml of 0 1 M Na S O3 The following readings were obtained EnK T in K 4 250K 333 33 K 500K 1000 K K is the rate constant in s 1 Find activation energy in kcal mole R 2 cal mol K 5 6

In a culture of bacteria a sample is taken at 10 00 AM and contains 1000 cells per ml A second sample at 8 00 PM has 10 000 cells per ml What is the generation time assuming first order overall growth log2 0 301

Question Number 143 Question Id 8135612223 Question Type MCQ Display Ques Number Yes Is Question Mandatory No Single Line Question Option No Option Orientation Vertical Identify the rate expression which obeys the condition the percentage of reaction rate increases when the concentration of reactant is doubled savas Sod usorrere udowod Options 1 7 K A 2 2 T K A K A 3 r 4 do when a woh den for Doreen 5 de uso r K A

entify the statements which is are incorrect from the following Rate of reaction increases substantially with increase in temperature since frequency of total collisions between reactant molecules increases Rate of reaction decreases on increasing temperature if the reaction is exothermic Rate of reaction remains unchanged if temperature changes for reactions having no activation energy barrier Rate of reaction decreases on decreasing temperature only if the reaction is endothermic

Question Number 152 Question Id 8135612232 Question Type MCQ Display Question Number Yes Is Question Mandatory No Single Line Question Option No Option Orientation Vertical For a 2nd order reaction rate at a particular time is x If the initial concentration is tripled the rate will become as jau stros ojs as waves de x sairasse cours de es dog dew Dovod Options 1 3x 2 9x 3 27x

For a certain chemical reaction variation in the concentration log R Vs time plot is given below i What is the order of reaction ii What are the units of rate constant k iii Give the relationship between k and t2 half life period iv What is the slope of the curve v Draw the plot of log R o R Vs time t log R t s X

55 For zero order reaction A 3B plot of concentration vs time is as follows Answer 8 4 t min Find half life period in minutes if the initial concentration of A be 1 M Explanation Conc Your Answer 0 2 Accepted error 0 0000 6 B A 8

For an endothermic reaction energy of activation is E and enthalpy of reaction is AH both of these in kJ mol Minimum value of Ea will be a less than AH c more than AH b equal to AH d equal to zero

In an elementary reaction A 2B 2C D If the concentration of A is increased four times and B is decreased to half of its initial concentration then the rate becomes 1 Twice 2 Half 3 Unchanged

In any chemical reaction equilibrium is supposed to be established when 1 Mutual opposite reaction undergo 2 concentration of reactants and resulting products are equal 3 Velocity of mutual reactions become equal 4 The temperature of mutual opposite reactions becomes equal

3 N O5 decomposes to NO and O and follows first order kinetics After 50 minutes the pressure inside the vessel increases from 50 mm Hg to 87 5 mm Hg The pressure of the gaseous mixture after 100 minutes at constant temperature will be a 116 25 mm Hg c 106 25 mm Hg b 175 0 mm Hg d 136 25 mm Hg

The mechanism 2NO F i NO ii F O NO iii F NO Select the correct one A B of the reaction 2NO F is Slow C D fast NO O fast the reaction is of 3rd order NO F F NO F the molecularity of the reaction is sum of molecularities of all steps reaction is zero order w r t F half life of reaction depends upon initial conc of NO

So 1 The following results were obtained during kinetic studies of the reaction 24 B products Exp A B in mol L in mol L 0 10 I II III The time in minutes a 5 b 1 0 10 0 20 0 20 0 25 0 30 Initial rate of reaction in mol L min 6 93 10 3 6 93 10 3 1 386 10 required to consume half of A is c 10 d 100

Freezing point of pure liquid A is T K If some amount of non electrolyte non volatile impurity is added in A an ideal solution is formed On cooling at 200 K only 30 by mass liquid A is present and at 201 K 60 by mass liquid A is present The value of T is 1 199 3 204 2 202 4 206

A first order reaction had started with 10 M of reactant A 96 875 of A got consumed in 500 sec Then the rate of reaction at the end of 500th sec will be in mole L sec A 0 225 x 10 B 0 693 C 0 0693 D 0 125 x 10

ere was initially 100mg of radioactive material After 6 hours its mass decreased by 3 If at any instance its disintegration is proportional to the quantity of material present determine how much is left after 24 hours

decreases by a factor of 4 reactant B is doubled The order of this reaction with respect to reactant B is 2005 a 1 b 2 c 1 d 2 1 For a first order reaction A B the reaction rate at reactant concentration of 0 01 M is found to be 2 0 x 105 mol L s The half life period of the reaction is 2005 a 227 s b 327 s c 527 s d 347 s

of reactant is 10 mol L rate of disappearance of A is found to be 2 x 10 mol L s If concentration of reactant is increased 16 times then rate of reaction increases four fold If rate constant of reaction is x 100 find x O 1 02 O 3

Using the following diagram select the correct relation AH A B AH C AH3 AH D O AH AH AH3 AH4 O AH AH3 AH AH4 O AH4 AH AH AH3 hr min O AH4 AH3 AH AH

3 The gas phase decomposition 2N2O5 4NO2 O2 follows the first order rate law K 7 5 10 sec The initial pressure of N2O5 is 0 1 atm The time of decomposition of N2O5 so that the total pressure becomes 0 15 atm will be A 54 sec C 3 45 sec B 5 4 sec D 34 55 sec

If value of Kc 6 8 x 10 27 then which of the following statement is correct O Reaction hardly proceeds O Reaction proceeds almost to completion Both the reactants and products are present in appreciable amount at equilibrium O Extent of reaction is very large

13 The molecularity of a complex reaction given below is AREACTION MECHANISM 2N205 8 IS REQUIRED b 2 DOUBT a 1 4NO g O g c 3 d has no mea

Consider a reaction A g select correct graph a 0 5M B 1 0M B 5 10 time in min 5 10 time in min k 0 1 M min 1 2B g If initial concentration of A is 0 5M then X k COMME b 1 0M B 0 5M 2 0M ese 1 0M A 5 10 time in min d B 5 10 time in min 3 21 1 00 Smin

A g 2B 2C g 2 the partial pressure of A and B at equilibrium are 0 80 atm and 0 40 atm respectively The pressure of the system is 2 80 atm The equilibrium constant K will be P b 5 0 a 20 c 0 02 d 0 2

A saturated solution in AgA Ksp 3x10 14 and AgB Kp 1 10 14 has conductivity of 375 x 10 10 Scm Limiting molar conductivity of Ag and A are 60 Scm mol and 80 Scm mol respectively If the limiting molar conductivity of B is Y Y in Scm mol Find out the value of 54 sp

The reaction X product follows first order kinetics In 40 minutes the concentration of X changes from 0 1M to 0 025M then the rate of reaction when concentration of X is 0 01M is 1 3 47x10 M min 2 1 73x10 M min 3 1 73x10 M min 4 3 47x10 M min The enthalpy of vapourization of a liquid is 30 kJ mol and entropy of vapourization is 75J mol K

Suppose that a gas phase reaction 2A g 2B g C g follows second order kinetics and goes to completion If the reaction is allowed to proceed in a constant volume vessel at an initial pressure of 4 bar only A is initially present The total pressure of the reaction mixture at t 00 is 2 Points 1

3 Increase in the average molecular speed 4 Decrease in mean free path 2 Calculate the average life in minutes if the half life of a radionuclide is 69 3 minutes 1 100 2 1 100 3 69 3x14 4 4 0 693 69 3

0 Consider the reaction H C H4 C H6 The molecular diameters of H and C H are 1 8 and 3 6 respectively The pre exponential factor in the rate constant calculated using collision theory in m mole s is approximately N 1 11 1027 m mole s where the symbols have For this reaction at 300 K their usual meanings 8kgT TELL

20 mL of a solution of H O2 of 10 volume strength decolourises 150 mL of KMnO4 solution acidified with dil H SO4 The amount of KMnO4 in the given solution is K 39 Mn 55 A 0 524 g B 1 125 g c 1 128 g

28 If the rate of reaction is 2 6 10 mol L s at 50 C and 7 02x10 mol L s at 80 C then what will be the temperature coefficient of the reaction 29 How many number of following ions for which all octahedral complexes are paramagnetic irrespective of ligand

mple 4 9 tion rate constants of a reaction at 500K and 700K are 0 02s and 0 07s respectively Calculate the values of E and A Since k log k 0 07 0 02 0 544 log E T T 2 303R TT E 7 700 500 700x500 2 303x8 314 JK mol Ex 5 714 x 10 19 15 0 544 x 19 15 5 714 x 10 18230 8 J k Ae Ea RT 0 02 Ae 18230 8 8 314 500 A 0 02 0 012 1 61 mple 4 10 The first order rate constant for the decomposition of ethyl iodide by the reaction C H I g C H g HI g

At constant temperature and volume X decomposes as 2X g Px is the partial pressure of X Observation number Time in minute 0 1 2 100 3 200 i What is the order of reaction with respect to X ii Find the rate constant iii Find the time for 75 completion of the reaction iv Find the total pressure when pressure of X is 700 mm of Hg 3Y g 2Z g P in mm of Hg 800 400 200 2005

The solubility of CaCO3 is 8mg L Calculate the Ksp of BaCO3 when Na2CO3 is added slowly a solution containing equimolar concentration of Ca and Ba and no precipitate is formed until 80 of Ba has been precipitated as BaCO3 2 A 1 1 x 10 10 B 5 0 x 10 1 10 C 6 4 x 10 10

The rate constant of a second order reaction is 5 70x10 5 dm mol 1 s 1 at 25 C and 1 64x10 4 dm mol s1 at 40 C calculate the activation energy and the arrhenius pre exponential factor

The rate constant of a reaction Activation energy E increases twice as fast as the rate constant of a sec reaction Activation energy E with temperature Which of the following conditions will hold good Assu same value of pre exponential factor 1 E E 2 E E 1 U 1 F

A 2B CA 2B C whose rate at 25 C C was measured using three different sets of initial concentrations as listed in the following table Trial A A B B Rate 1 MM MM M sM s 0 40 0 0305 8 10 3 0 40 0 0601 2 10 2 0 80 0 0302 3x10 2 2 3 What is the rate law for this reaction Express the rate law symbolically in terms of kk A A and B B

For a gaseous phase reaction 2A g 3B g Pressure 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

5 Mechanism of a hypothetical reaction 2017 Delhi X Y 2XY is given below i X X X fast ii X Y XY Y slow iii X Y XY fast The overall order of the reaction will be a 1 5 b 1 c 2 d 0

Identify the correct statement regarding enzymes 1 enzymes are specific biological catalysts cannot be poisoned 2 enzymes are specific biological catalysts that possess well defined active sites 3 enzymes are specific biological catalysts than can normally function at very hig temperatures T 1000K 4 enzymes are normally heterogeneous catalysts that are very specific in their action The increasing order of the pk values of the following compounds is OU QU OH QU