JEE Main Previous Year Papers Questions With Solutions Chemistry Kinetics,Catalysis and Surface Chemistry

1.Units of rate constant of first and zero order  reactions in terms of molarity M unit are respectively       (2002)
1) sec-1, Msec-1                       2) sec-1, M
3)Msec-1, sec-1             4) M, sec-1

Ans.
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2.For the reaction A + 2B—— > C, rate is given  by R = [A] [B]2 then the order of the reaction is (2002)
1) 3                       2) 6                         3) 5                         4) 7

Ans.(1) Order is the sum of the power of the concentrations terms in rate law expression.

3.The formation of gas at the surface of tungsten due to adsorption is the reaction of order  (2002)
1) 0                       2) 1                         3) 2                  4)insufficient data

Ans.(1) It is zero order reaction

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Ans.(4) Rate of appearance of HI is twice to that of disappearance of H1 or I1

5.If half-life of a substance is 5 years, then the total amount of substance left after 15 years, when initial amount is 64 grams is (2002)
1) 16 grams                                     2) 2 grams
3) 32 grams           4) 8 grams

Ans.
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Ans.(1) time versus log concentration

7.The internal energy change when a system goes from state A to B is 40 kJ/mol-1. If the system goes from A to B by a reversible path and returns to state A by an irreversible path. What would be the net change in internal energy ?     (2003)
1) > 40 kJ 2) <40 kJ 3) Zero 4) 40 kJ

Ans.(3) For a cyclic process the net change in the internal energy is zero because the change in internal energy does not depend on the path.

8.The half-life of a radioactive isotope is three  hours. If the initial mass of the isotope were 256g, the mass of it remaining undecayed after 18 hours would be   (2003)
1) 8.0 g 2) 12.0 g 3) 16.0 g 4) 4.0 g

Ans.
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9.Which one of the following characteristics is not correct for physical adsorption ? (2003)
1)Adsorption increases with increase in temperature
2)Adsorption is spontaneous
3)Both enthalpy and entropy of adsorption are negative
4)Adsorption on solids is reversible

Ans.(1) As adsorption is an exothermic process. Rise in temperature will decrease adsorption.

10.In respect of the equation k = Ae-Ea/RT in  chemical kinetics, which one of the following statements is correct ?         (2003)
1)A is adsorption factor
2)Ea is energy of activation
3)R is Rydberg’s constant
4)k is equilibrium constant

Ans.(2) A is pre exponential facter,E is activation energy, R is gas constant and K is rate constant.

11.The rate law for a reaction between the substances  A and B is given by Rate = k[A]n[B]m. On doubling the concentration of A and halving the concentration of B, the ratio of the new rate to the earlier rate of the reaction will be as (2003)
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Ans.
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Ans.(2) r=k[02][N0]2. When the volume is reduced to half, the cone, will double.  New rate = k[202][2NO]2 = 8k[02][NO]2. The new rate increases by eight times.

13.In first order reaction, the concentration of  the reactant decreases from 0.8 M to 0.4 M in 15 minutes. The time taken for the concentration to change from 0.1 M to 0.025 M is   (2004)
1) 30 minutes                               2) 60 minutes
3) 7.5 minutes                             4) 15 minutes

Ans.(1) t1/2 = 15 minutes Number of half lives =2 (For change of 0.1 to 0.05 and then to 0.025) Total time is 30 minutes

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Ans.(2) Second order reaction.

15.Identify the correct statements regarding  enzymes  (2004)
1)Enzymes are specific biological catalysts that can normally function at very high temperature
2)Enzymes are specific biological catalysts that the posses well – defined active sites
3)Enzymes are specific biological catalysts that can not be poisoned
4)Enzymes are normally heterogeneous catalysts that are very specific in their action

Ans.(2) Enzymes are specific catalysts at room m

16.The half – life of a radioisotope is four hours.  If the initial mass of the isotope was 200 g, the mass remaining after 24 hours undecayed is         (2004)
1)042 g                        2) 4.167 g
3) 3.125 g                                         4) 2.084 g

Ans.
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17.Consider an endothermic reaction, X—— > Y  with the activation energies Eb and Ef for the backward and forward reactions, respec ­tively. In general (2005)
1)Eb < Ef           2) Eb > Ef
3)Eb = Ef
4)There is no definite relation between Eb and Ef

Ans.
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18. The volume of a colloidal particle, Vc as compared to the volume of a solute particle  in a true solution Vs,could be  (2005)
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Ans.
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19.The disperse phase in colloidal iron (III) hydroxide and colloidal gold is positively and negatively charged, respectively, which of the  following statements is NOT correct? (2005)
1)magnesium chloride solution coagulates, the gold sol more readily than iron (III) hydroxide sol.
2)sodium sulphate solution causes coagulation in both sols
3)mixing the sols has no effect
4)coagulation in both sols can be brought about by electrophoresis

Ans.(3) Same coagualtion occurs.

20. t1/4 can be taken as the time taken for the  concentration of a reactant to drop to 3/4 of its initial value. If the rate constant for a first order reaction is K, the t1/4 can be written as  (2005)
1)10 / K                         2) 0.29/K
3) 0.69 / K                                       4) 0.75 / K

Ans.
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21.A reaction involving two different reactants  can never be  (2005)
1)Unimolecular reaction
2)First order reaction
3)second order reaction
4) Bimolecular reaction

Ans.(1) Only one reactant is involved in unimolecular reaction.

22.A reaction was found to be second order with  respect to the concentration of carbon monoxide. If the concentration of carbon monoxide is doubled, with everything else kept the same, the rate of reaction will (2006)
1)remain unchanged                       2) triple
3) increase by a factor of 4                           4) double

Ans.
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23.In Langmuir’s model of adsorption of a gas  on a solid surface    (2006)
1)the rate of dissociation of adsorbed molecules from the surface does not depend on the surface covered
2)the adsorption at a single site on the surface / may involve multiple molecules at the same  time
3)the mass of gas striking a given area of surface is proportional to the pressure of the gas
4)the mass of gas striking a given area of surface is independent of the pressure of the gas

Ans.(3) The extent of adsorptions is directly proportional to the pressure of gas.

24.Rate of a reaction can be expressed by Arrhenius equation as: k=Ae-E /RT  In this equation, E represents (2006)
1)the energy above which all the colliding molecules will react
2)the energy below which colliding molecules will not react
3)the total energy of the reacting molecules at a temperature, T
4)the fraction of molecules with energy greater than the activation energy of the reaction

Ans.(2) Colliding molecules with energy less than activation energy with not react.

25.Consider the reaction, 2A+B —> Products. 5  When concentration of B alone was doubled, i. the half-life did not change. When the con ­centration of A alone was doubled, the rate increased by two times. The unit of rate con ­stant for this reaction is               (2007)
1) L mol-1 s-1          2) No unit
3) molL-1 sy1          4) s-1

Ans.(1) 2A + B-> Product  When cone, of B is doubled, the half life did „ not change, hence reaction is of first order w.r.t.  When concentration of A is doubled, reaction rate is doubled, hence reaction is of first order w.r.t. A. Hence over all order of reaction is 1 + 1=2 .So, unit of rate constant mol-1 fits-1.

26.A radioactive element gets spilled over the floor of a room. Its half-life period is 30 days.If the initial activity is ten times the permis ­sible value, after how many days will it be safe to enter the room ?  (2007)
1) 1000 days                               2) 300 days
3) 10 days                                       4) 100 days

Ans.
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Ans.
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28.Gold numbers of protective colloids A, B, C and D are 0.50, 0.01, 0.10 and 0.005, respectively. The correct order of their protective powers is (2008)
1)D<A<C<B           2)C<B<D<A
3)A<C<B<D           4)B<D<A<C

Ans.(3) Higher the gold number lesser will be the protective power of colloid.

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Ans.(4) Enthalpy of adsorption regarding physisorption is not positive and it is negative.

30.The half life period of a first order chemical reaction is 6.93 minutes. The time required for the completion of 99% of the chemical reaction will be (log 2 = 0.301) : (2009)
1) 230.3 minutes                     2) 23.03 minutes
3) 46.06 minutes                     4) 460.6 minutes

Ans.
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31.The time for half life period of a certain reaction A products is 1 hour. When the initial concentration of the reactant ‘A’, is 2.0 molL-1, how much time does it take for its concentration to come from 0.50 to 0.25 mol Lr1 if it is zero order reaction? (2010)
1) 4h 2) 0.5h                                 3) 0.25h             4) lh

Ans.
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Ans.
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33.The rate of a chemical reaction doubles for  every 10 °C rise of temperature. If the temperature is raised by 50 °C, the rate of the reaction increases by about      (2011)
1) 32 times 2) 64 times 3) 10 times 4) 24 times

Ans.
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Ans.
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35.For a first order reaction, (A) —> products, the concentration of A chnages from 0.1 M to 0.025 M in 40 minutes. The rate of reaction when the concentration of A is 0.01 M  (2012)
1) 1.73 x 10-5 M/ min 2) 3.47 x 10-4 M / min 3) 3.47 x 10-5 M / min 4) 1.73 x 10-4  M / min

Ans.
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36.The rate of a reaction doubles when its  temperature changes from 300K to 310K. Activation energy of such a reaction will be (R = 8.314 JK ‘mol-1 and log 2 = 0.301)(2013)
1) 53.6 kJ mol-1                   2) 48.6kJmol-1
3) 58.5 kJmol-1              4) 60.5 kJmol-1

Ans.
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Ans.(2) Coagulation power increases with increase in charge of cation.

38.For the non-stoichiometry reaction  2A + B C + D, the following kinetic data were obtained in three separate experiments, all at 298 K.    (2014)
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Ans.(1) Rate = K(A)m (B)m

39.Higher order (>3) reactions are rare due to(2015)
1)low probability of simultaneous collision of all the reacting species
2)increase in entropy and activation energy  as more molecules are involved
3)shifting of equilibrium towards reactants due to elastic collisions
4)loss of active species on collision 40.

Ans.(1) According to collision theory

40.3 g of activated charcoal was added to 50 ml. of acetic acid solution (0.06N) in a flask. After qan hour it was filered and the strength of type nitrate was found to be 0.042 N. The amount of acetic acid absorbed (per gram of charcoal) is (2015)
1) 18 mg 2) 36 mg 3) 42 gm 4) 54 .mg

Ans.
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