MCQ ON NUCLEAR CHEMISTRY

is the more stable isotope of Na. Find out the process by which can undergo radioactive decay [IIT Screening 2003] (a) emission (b) emission (c) emission (d) K electron capture Oxygen contains 90% of and 10% of . Its atomic mass is [KCET 1998] (a) 17.4 (b) 16.2 (c) 16.5 (d) 17 The missing particle in the reaction, is [DPMT 2001] (a) (b) (c) (d) Sulphur-35 (34.96903 amu) emits a particle but no rays, the product is chlorine-35 (34.96885 amu). The maximum energy emitted by the particle is [DPMT 2004] (a) 0.016767 MeV (b) 1.6758 MeV (c) 0.16758 MeV (d) 16.758 MeV A radioactive substance has a constant activity of 2000 disintegration/minute. The material is separated into two fractions, one of which has an initial activity of 1000 disintegrations per second while the other fraction decays with = 24 hours. The total activity in both samples after 48 hours of separation is [JIPMER 2000] (a) 2000 (b) 1250 (c) 1000 (d) 1500 How many alpha particles are emitted per second by 1 microgram of radium (a) (b) (c) (d) If 1 microgram of radium has disintegrated for 500 years, how many alpha particles will be emitted per second (a) (b) (c) (d) A radioactive nucleide X decays at the rate of disintegration . Radium decays at the rate of disintegration . The activity of X in millicuries is [MP PET 2001] (a) 0.027 (b) (c) 0.00270 (d) 0.000270 If nucleus absorbs a neutron and disintegrates in , and X, then what will be the product X [CBSE 2002] (a) (-particle (b) (-particle (c) 2-neutrons (d) 3-neutrons The half-life of a radioactive isotope is 3 hours. Value of its disintegration constant is [BHU 2002] (a) 0.231 per hr (b) 2.31 per hr (c) 0.2079 per hr (d) 2.079 per hr The activity of carbon-14 in a piece of an ancient wood is only 12.5%. If the half-life period of carbon-14 is 5760 years, the age of the piece of wood will be [MP PMT 1999] (a) years (b) years (c) years (d) years The radium and uranium atoms in a sample of uranium mineral are in the ratio of . If half-life period of radium is 1620 years, the half-life period of uranium will be [MP PMT 1999] (a) years (b) years (c) years (d) years Half-life of radium is 1580 yrs. Its average life will be [AIIMS 1999; AFMC 1999; CPMT 1999] (a) (b) (c) (d) 8 gms of a radioactive substance is reduced to after 1 hour. The of the radioactive substance is [DCE 2000] (a) 15 min (b) 30 min (c) 45 min (d) 10 min A first order nuclear reaction is half completed in 45 minutes. How long does it need 99.9% of the reaction to be completed [KCET 2001] (a) 5 hours (b) 7.5 hours (c) 10 hours (d) 20 hours Number of (--particles emitted per second by a radioactive element falls to 1/32 of its original value in 50 days. The half-life-period of this elements is [AMU 2001] (a) 5 days (b) 15 days (c) 10 days (d) 20 days What is the half-life of a radioactive substance if 87.5% of any given amount of the substance disintegrates in 40 minutes [Kerala CET 1996] (a) 160 min (b) 10 min (c) 20 min (d) 13 min 20 sec A radioactive isotope has a of 10 days. If today 125 gm of it is left, what was its weight 40 days earlier [EAMCET 1991] (a) (b) (c) (d) The half-life of , if its decay constant is is [CBSE PMT 2001] (a) 1098 yrs (b) 109.8 yrs (c) 10.98 yrs (d) 1.098 yrs A radioactive sample has a half-life of 1500 years.A sealed tube containing of the sample will contain after 3000 years [MNR 1994; UPSEAT 2001, 02] (a) of the sample (b) of the sample (c) of the sample (d) of the sample The half-life of a radioactive isotope is three hours. If the initial mass of the isotope were 256 g, the mass of it remaining undecayed after 18 hours would be [AIEEE 2003] (a) 4.0 g (b) 8.0 g (c) 12.0 g (d) 16.0 g of a radioactive sample decays in 40 days half-life of the sample is [DCE 2001] (a) 100 days (b) 10 days (c) 1 day (d) 2 days A radioactive element with half-life 6.5 hrs has atoms. Number of atoms left after 26 hrs [BHU 2003] (a) (b) (c) (d) The half-life of 1 gm of radioactive sample is 9 hours. The radioactive decay obeys first order kinetics. The time required for the original sample to reduce to 0.2 gm is [AMU (Engg.) 2002] (a) 15.6 hours (b) 156 hours (c) 20.9 hours (d) 2.09 hours The half-life period of a radioactive substance is 140 days. After how much time 15 g will decay from 16 g sample of it [AFMC 2002] (a) 140 days (b) 560 days (c) 280 days (d) 420 days Percentage of a radioactive element decayed after 20 sec when half-life is 4 sec [BHU 2003] (a) 92.25 (b) 96.87 (c) 50 (d) 75 Consider an (-particle just in contact with a nucleus. Calculate the coulombic repulsion energy (i.e. the height of the coulombic barrier between and alpha particle) assuming that the distance between them is equal to the sum of their radii [UPSEAT 2001] (a) 23.8517× (b) (c) (d) The half-life period of is 22 years. If 2 gm of is taken, then after 11 years how much of will be left [KCET 2001] (a) 1.414 gm (b) 2.428 gm (c) 3.442 gm (d) 4.456 gm A wood specimen from an archeological centre shows a activity of 5.0 counts/min/gm of carbon. What is the age of the specimen for is 5000 years) and a freshly cut wood gives 15 counts/min/gm of carbon [AMU (Engg.) 2002] (a) years (b) years (c) years (d) years fission product+neutron. The energy released when of undergoes fission is [CBSE PMT 1997] (a) (b) (c) (d) The triad of nuclei that is isotonic is [IIT 1988; DCE 2000;MP PMT 2004] (a) (b) (c) (d) The relative abundance of two isotopes of atomic weight 85 and 87 is 75% and 25% respectively. The average atomic weight of element is [DCE 2003] (a) 75.5 (b) 85.5 (c) 40.0 (d) 86.0 1. (a) so decrease in ratio gives out -particle . 2. (b) Oxygen have 90% and 10% Atomic mass = = . 3. (c) It is a neutron induced fission reaction. 4. (a) Mass defect = mass of sulphur – mass of chlorine Binding energy =mass defect 931 5. (a) The problem refers that rate is constant. 6. (a) = Activity of of Activity of of So, the no. of -particles are emitted per second by of is 7. (a) (-particles will be emitted per second. 8. (b) . 9. (d) 10. (a) per hrs. 11. (b) of C–14 = 5760 year, Now = 17281= 172.81 × years. 12. (c) According to radioactive equilibrium or Where and are half periods of A and B respectively At equilibrium A and B are present in the ratio of their half lives Half-life of uranium = years. 13. (c) Average life period = 14. (a) N = 0.5g and t = 1 hr. = 60 min. find by . 15. (b) . 16. (c) T = 50 days, = ?, or or or n = 5 , or days. 17. (d) = 0.693/0.05199 = 13.33 min. = 13 min 20 sec. 18. (d) Calculate as, . 19. (a) . 20. (c) ( (n = 2 ( Amount left . 21. (a) , . 22. (b) Quantity of radioactive element decayed Quantity left = or one half-life = days. 23. (c) . 24. (c) 25. (b) 26. (b) . 27. (b) where A is mass number (Total distance in between uranium and nuclei = 8. 06× + 2.06 × = 10.12 × cm Now repulsion energy = = = 28. (a) [= 22 years, T = 11 years, =2, =?] 11= 2 × n or . 29. (c) 30. (c) 1g U-235 energy released . 31. (a) Isotones have same number of neutrons. 32. (b) Average atomic weight of element NUCLEAR CHEMISTRY Mrs. SHALLU JINDAL AGGARWAL : (M)9878608983