MCQ on Chemical Kinetics & Nuclear & Radio Chemistry

Chemical Kinetics and Nuclear and Radio chemistryQuestions: 1. Pieces of wood burn faster than a log of wood of the same mass because (a) surface area of log of wood is larger and needs more time to burn (b) pieces of wood have large surface area (c) all pieces of wood catch fire at the same time (d) block of wood has higher density than pieces of the same wood. 2. Which of the following does not affect the rate of reaction? (a) amount of the reactions taken (b) physical state of the reactions (c) of reaction (d) size of the vessel 3. The reaction 2 NO + O2 2 NO2 2 CO + O2 2 CO2 look to be identical, yet the first is faster than the second. The reason is that (a) The first reaction has lower enthalpy change than the second (b) The first reaction has lower internal energy change than the second. (c) The first reaction has lower activation energy than the second. (d) The first reaction has higher activation energy change than the second. 4. Oxalic acid is oxidized by acidified KMnO4 as follows: The rate of this reaction increases with time because CO2 formed escapes Of presence of sulphuric acid () Of formation of which acts as an auto catalyst KMnO4 is a strong oxidizing agent. 5. An exothermic chemical reaction occurs in two steps as follows: (i) A + B X (fast); (ii) X AB (slow); The progress of the reaction can be best represented by 6. In the reaction 2A + B products, the order w.r.t. A is found to be one and w.r.t. B equal to 2. Concentration of A doubled and that of B is halved, the rate of reaction will be (a) doubled (b) halved (c) remain unaffected (d) four times 7. When concentration of reactant in reaction A B is increased by 8 times, the rate increases only 2 times. The order of the reaction would be (a) 2 (b) 1/3 (c) 4 (d) ½ 8. In the decomposition of N2O5, the rate of reaction is For determination of the units of k, units of the time are required Units of the concentration are required Units of both time and concentration are required None of these 9. While the studying the decomposition of gaseous N2O5, it is observed that a plot of logarithm of its partial pressure versus time is linear. The kinetic parameter obtained from this observation is (a) Specific rate of reaction (b) Reaction rate (c) Energy of activation (d) Molecularity 10. For the reaction, A b, the rate of reaction is quadrupled when the concentration of a is doubled the rate expression of the reaction is , when the value of n is (a) 1 (b) zero (c) 3 (d) 2 11. Half life period of 2nd order reaction is: (a) proportional to initial conc. of reactants. (b) Independent of initial concentration of reactants (c) inversely proportional initial concentration of reactants. (d) inversely proportional to of initial concentration of reaction 12. The half life period of a zero period reaction is (a) directly proportional to initial concentration (b) inversely proportional to initial concentration (c) independent of initial concentration (d) proportional to the square of initial concentration 13. According to collision theory of reaction rates of reaction depends (a) Only upon the total number of collisions per second (b) Only upon the colliding molecules with energy greater than threshold energy (c) Upon the ordination of molecules at the time of collision (d) Both (b) and (c) 14. The activation energy of reaction is equal to (a) Threshold energy for the reaction (b) Threshold energy + Energy the reactants (c) Threshold energy - Energy the reactants (d) Threshold energy + Energy the products 15. The presence of a catalyst (a) Increase the heat of reaction (b) Decrease the heat of reaction (c) Has no effect on the heat of reaction (d) Has no effect on the energy of activation 16. Which of the following explain the increase of reaction rate by a catalyst (a) Catalyst provides the necessary energy to the collides molecules to cross the barrier. (b) Catalyst decreases the rate of backward reaction so that the rate of forward reaction increase (c) Catalyst decrease the enthalpy change of the reaction (d) Catalyst provides an alternative path of lower activation energy 17. The enzyme catalyzed reaction is faster that a metal catalyzed reaction because (a) Its activation energy is greater (b) Its activation energy is lower (c) enzymes are present in larger amounts (d) none of the above 18. Which of the following expression give the effect of temperature on the rate constant? (a) In k = In A – Ea / RT (b) In k = In A + Ea / RT (c) In k = A – Ea / RT (d) In k = In A – In Ea / RT 19. The plot of log k vs helps to calculate (a) Energy of activation (b) Rate constant of the reaction (c) Order of the reaction (d) Energy of activation as well as the frequency 20. Photochemical reactions are those which takes place (a) At high temperatures (b) In presence of light only (c) In photography only (d) take place in presence of a suitable catalyst only 21. Which of the following statement is incorrect? (a) The catalyst does not affect the equilibrium of a reaction (b) Reaction with higher activation energy hag higher rate constant (c) In an exothermic reaction, the activation energy of the reverse reaction is higher than that of the forward reaction. (d) half period of a first order reaction is independent of initial concentration. 22. When ethyl acetate was hydrolysed presence of 0.1 N HCl, the rate constant was found to be 5.40 10-5 s-1. But when 0.1 N H2SO4 was used for the hydrolysis, the rate constant was found to be 6.20 10-5 s-1. From these values we can say that. (a) H2SO4 is stronger than HCl (b) H2SO4 is weaker than HCl (c) Both the acids have equal strength (d) The data is insufficient to compare the strength of HCl and H2SO4. 23. The second order rate constant is usually expressed as (a) Mole litre sec-1 (b) Mole-1 litre-1 sec-1 (c) Mole litre-1 sec-1 (d) Mole-1 litre sec-1 24. If the concentration is expressed in moles per litre, the unit of the rate constant for the first order reaction is (a) Mole litre-1 sec-1 (b) Mole litre-1 (c) sec-1 (d) Mole-1 25. Which of the following is a first order reaction? (a) (b) 2 HI H2 + I2 (c) 2 NO2 2 NO + O2 (d) 2 NO + O2 2 NO2 26. The rate constant of a reaction increases with increase of temperature because (a) The activation energy increases (b) The population of activation molecules increases (c) The activation energy decreases (d) The population of activated molecules decreases. 27. In the reaction 2 NO + Cl2 2 NOCl, it has been found that doubling the concentration of the both the reactants increases the rate of factor of eight but doubling the chlorine concentration alone only doubling the rate. Which of the following statement is incorrect? (a) The reaction is first order in Cl2 (b) The reaction is first order in NO (c) The over all order of reaction is 2 (d) The over all order of reaction is 3 28. For the half life period of a first order reaction, which one of the following statements is generally false? (a) It is independent of initial concentration (b) It is independent of temperature (c) It is decrease with the introduction of a catalyst (d) It decreases with increases of temperature 29. An isotope of parent element is produced when in loses (a) one -particle only (b) one and one particles (c) Two and Two particles (d) one and Two particles 30 . Average life period is equal to (a) (b) (c) (d) 0.75 31. The average life ()of a radioactive element is equal to (a) half-life period (b) disintegration constant (c) One half of the disintegration constant (d) 1.44 times of the half-life period 32. Neutrons are more effective projectiles than protons because they (a) are attracted by the nuclei (b) are not repelled by the nuclei (c) travel with high speed (d) none of above 33. The isotope is transformed into the isotope by a nuclear reaction. The nuclear reaction would involve. (a) -particle emission (b) -particle emission (c) neutron emission (d) emission of -rays. 34. The missing projectile in the reaction, (a) Proton (b) deuteron (c) positron (d) -particle 35. For the nuclear reaction, , the missing nuclide is (a) (b) (c) (d) 36. Which of the following is an exact example of artificial radioactivity? (a) (b) (c) (d) . 37. The phenomenon of nuclear fisson was experimentally observed by (a) Fermi (b) Becquerel (c) Strassman (d) Planck 38. The easily fissionable isotope to uranium is with mass number (a) 235 (b) 236 (c) 237 (d) 238 39. Which of the following is not transuranic element? (a) Pu (b) Bi (c) Cm (d) Am 40. The radioactive isotope of carbon used in radio carbon dating is (a) (b) (c) (d) 41. Which of the following is used in dating archaeological findings? (a) (b) (c) (d) 42. in the upper layer of the atmosphere is produced by the action of neutrons on. (a) (b) (c) (d) 43. Neutrino can be detected during the emission of (a) - rays (b) -particles (c) protons (d) X- rays. 44. The nucleus of an atom is made up of X protons and Y neutrons. For the most stable and abundant nuclei (a) X and Y are both even (b) X and Y are both odd (c) X is even and Y is odd (d) X is odd and Y is even 45. Which of the following transformation is incorrect? (a) (b) (c) (d) 46. Which metal Aprons are worn by radiographer to protect him from radiation (a) Mercury Coated Apron (b) Lead Apron (c) Copper Apron (d) Aliminmised Apron 47. Which of the following isotope of uranium is the most radioactive? (a) 235 (b) 236 (c) 237 (d) 238 48. A radioactive element X emits 3 , 1 and 1 - particle and forms Element X is (a) (b) (c) (d) 49. A radioactive sample has half life of 1500 years. A sealed tube containing 1 g of a sample will contain…g of the sample after 3000 years. The missing figure is (a) 1g (b) 0.5 g (c) 0.25 g (d) 0 g 50. Thorium disintegration series is known as (a) (4n +2) series (b) (4n+3) series (c) 4n series (d) (4n+1) series 51. Number of neutrons in a parent nucleus X, which gives after two successive emission, would be (a) 6 (b) 7 (c) 8 (d) 9 52. What is the half life of a radioactive substance if 87.5% of any given amount of the substance disintegrates in 40 minutes? (a) 160 min (b) 10 min (c) 20 min (d) 13 min 20 sec 53. Half life of a radioactive substance which disintegrates by 75% in 60 minutes will be: (a) 120 min (b) 30 min (c) 45 min (d) 20 min 54. A certain nuclide has a half life of 60 minutes. If a sample containing 600 atoms is allowed to decay for 90 minutes, the atom remaining will be nearly (a) 200 (b) 75 (c) 450 (d) 50 55. The half-life period of a radioactive material is 15 minutes. What percent of that radioactive material will remain after 45 minutes? (a) 10% (b) 12.5% (c) 15% (d) 17.5% 56. A radioisotope has of 10 days. If today 125g of it is left, what was its weight 40 days earlier? (a) 600 g (b) 1000 g (c) 1250 g (d) 2000 g 57. The half life of is 20 years. If its sample having initial activity of 8000 dis/min is taken, what would be its activity after 80 years? (a) 500 dis/min (b) 800 dis/min (c) 1000 dis/min (d) 1600 dis/min 58. A radioactive isotope having a half-life of 3 days was received after 12 days. It was found that there was 3g of the isotope in the container. The initial weight of the isotope when placed was (a) 12 g (b) 24 g (c) 36 g (d) 48 g 59. The half life period of a radioactive element is 30 min. One sixteenth of the original quantity of the element will remain unchanged after. (a) One hour (b) Sixteen hours (c) Four hours (d) Tow hours 60. A radioactive element has a half-life of 20 mins. How much time should elapse before the element is reduced to the of the original mass? (a) 40 min (b) 60 min (c) 80 min (d) 160 min ***** Keys: 1 b 2 c 3 c 4 c 5 c 6 b 7 b 8 a 9 a 10 d 11 c 12 a 13 d 14 c 15 c 16 d 17 b 18 a 19 d 20 b 21 c 22 a 23 d 24 c 25 a 26 b 27 d 28 b 29 d 30 b 31 d 32 b 33 b 34 c 35 a 36 c 37 c 38 a 39 b 40 c 41 b 42 d 43 b 44 a 45 c 46 b 47 a 48 c 49 c 50 c 51 d 52 d 53 b 54 a 55 b 56 d 57 a 58 d 59 d 60 b Answers: 1. Larger the surface area, faster the reaction. 2. of a reaction has a no effect on the rate of reaction. 3. Lower the activation energy, faster is the reaction. 4. acts as an auto catalyst. 5. The reaction occurring in two steps has two activation energy peaks. The first step, being fast needs less activation energy. The second step, being slow, needs more activation energy. Therefore second peak will be higher than the first. 6. Rate k a b2. New rate = k (2a) 7. (i) r = k an (ii) 2r = k (8 a)n. Dividing (ii) by (i), 2 = 8n or 23n =1 or n = 1/3 8. Hence k = . 10. (i) Dividing (ii) by (i), 11. For the given reaction, molecularity is 2, order is 1. 12. . For zero order, n = 0. Hence . 13. Rate of reaction depends on energy factor and orientation factor. 14. Activation energy = Threshold energy- Energy of reactions. 15. Presence of catalyst has no effect on the heat of reaction. 16. Catalyst provides an alternative path of lower activation energy. 17. Enzyme catalyst reaction have lower activation energy. 18. In k = A – Ea / RT 19. Plot of log k vs 1 / T helps to calculate Ea and A. 20. Photochemical reaction takes place only in presence of light. 22. For equi-normal solution of the two acids 23. For 2nd order, 24. Units of rate constant for 1st order reaction are times-1. 25. Is a reaction of 1st order. 26. With increase in temperature, population of activated molecules increases. 27. (i) r = (ii) (iii) 2 r = Dividing (ii) by (iii), 4 = Dividing (iii) by (i), 2 = Overall order = 2 + 1 =3. 28. Half-life period depends on temperature. 29. Atomic no. remains the same but mass no. remains the same. 30. 31. . 32. Neutrons are not repelled because they are neutral. 33. 34. Missing projectile should be charge less and massless. 35. 36. Nucleus bombarded should be stable and nucleus produced should be radioactive. 37. A known fact. 38. U – 235 is fissionable. 39. Transuranic element have Z>92. 41. C -14 is used in radio carbon dating. 42. is produced by action of neutrons on . 43. Neutrino are neutral particles with negligible mass like -particles. 44. Nuclei which are most stable and abundant have been no. of protons and neutron because their spins tend to pair up. 45. In (c), Z and A are not equal on the two sides. 46. Radioactive iodine is to diagnose thyroid disorders. 47. Out of the given, U – 235 is most radioactive. 48. 49. 3000 yrs = Two half lives. Amount left = 50. Th-series is known as 4n series. 51. 52. = =13.33 min -13 min 20 sec. 53. 75% of the substance disintegrates in two half-lives. 2 half-lives = 60 min =30 min. 54. or or 55. . 56. or 57. n = 4, Activity after 4-half lives = = 58. 59. = 60. Chemical Kinetics And Nuclear and Radio chemistry 4 *** Mrs Shallu Aggarwal Mobile #. 98786-08983 ***