
question_answer1) \[_{11}^{23}Na\] is the more stable isotope of Na. Find out the process by which \[_{11}^{24}Na\] can undergo radioactive decay [IIT Screening 2003]
A) \[{{\beta }^{}}\]emission done
clear
B) \[\alpha \]emission done
clear
C) \[{{\beta }^{+}}\]emission done
clear
D) K electron capture done
clear
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question_answer2) Oxygen contains 90% of \[{{O}^{16}}\] and 10% of \[{{O}^{18}}\]. Its atomic mass is [KCET 1998]
A) 17.4 done
clear
B) 16.2 done
clear
C) 16.5 done
clear
D) 17 done
clear
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question_answer3) The missing particle in the reaction, \[_{92}^{235}U+_{0}^{1}n\,\to {{\,}_{56}}B{{a}^{146}}+...+3_{0}^{1}n\] is [DPMT 2001]
A) \[_{32}^{87}Ge\] done
clear
B) \[_{35}^{89}Br\] done
clear
C) \[_{36}^{87}Kr\] done
clear
D) \[_{35}^{86}Br\] done
clear
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question_answer4) Sulphur35 (34.96903 amu) emits a \[\beta \]particle but no \[\gamma \]rays, the product is chlorine35 (34.96885 amu). The maximum energy emitted by the \[\beta \]particle is [DPMT 2004]
A) 0.016767 MeV done
clear
B) 1.6758 MeV done
clear
C) 0.16758 MeV done
clear
D) 16.758 MeV done
clear
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question_answer5) 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 \[{{t}_{1/2}}\]= 24 hours. The total activity in both samples after 48 hours of separation is [JIPMER 2000]
A) 2000 done
clear
B) 1250 done
clear
C) 1000 done
clear
D) 1500 done
clear
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question_answer6) How many alpha particles are emitted per second by 1 microgram of radium
A) \[3.62\times {{10}^{4}}/\sec \] done
clear
B) \[0.362\times {{10}^{4}}/\sec \] done
clear
C) \[362\times {{10}^{4}}/\sec \] done
clear
D) \[36.2\times {{10}^{4}}/\sec \] done
clear
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question_answer7) If 1 microgram of radium has disintegrated for 500 years, how many alpha particles will be emitted per second
A) \[2.92\times {{10}^{4}}/\sec \] done
clear
B) \[292\times {{10}^{4}}/\sec \] done
clear
C) \[0.292\times {{10}^{4}}/\sec \] done
clear
D) \[29.2\times {{10}^{4}}/\sec \] done
clear
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question_answer8) A radioactive nucleide X decays at the rate of \[1.00\times {{10}^{5}}\] disintegration \[{{s}^{1}}{{g}^{1}}\]. Radium decays at the rate of \[3.70\times {{10}^{10}}\] disintegration \[{{s}^{1}}{{g}^{1}}\]. The activity of X in millicuries \[{{g}^{1}}\] \[(m\,ci\,{{g}^{1}})\] is [MP PET 2001]
A) 0.027 done
clear
B) \[0.270\times {{10}^{5}}\] done
clear
C) 0.00270 done
clear
D) 0.000270 done
clear
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question_answer9) If \[_{92}{{U}^{235}}\] nucleus absorbs a neutron and disintegrates in \[_{54}X{{e}^{139}}\], \[_{38}S{{r}^{94}}\] and X, then what will be the product X [CBSE 2002]
A) aparticle done
clear
B) bparticle done
clear
C) 2neutrons done
clear
D) 3neutrons done
clear
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question_answer10) The halflife of a radioactive isotope is 3 hours. Value of its disintegration constant is [BHU 2002]
A) 0.231 per hr done
clear
B) 2.31 per hr done
clear
C) 0.2079 per hr done
clear
D) 2.079 per hr done
clear
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question_answer11) The activity of carbon14 in a piece of an ancient wood is only 12.5%. If the halflife period of carbon14 is 5760 years, the age of the piece of wood will be \[(\log \,2=0.3010)\] [MP PMT 1999]
A) \[17.281\times {{10}^{2}}\] years done
clear
B) \[172.81\times {{10}^{2}}\] years done
clear
C) \[1.7281\times {{10}^{2}}\] years done
clear
D) \[1728.1\times {{10}^{2}}\] years done
clear
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question_answer12) The radium and uranium atoms in a sample of uranium mineral are in the ratio of \[1:2.8\times {{10}^{6}}\]. If halflife period of radium is 1620 years, the halflife period of uranium will be [MP PMT 1999]
A) \[45.3\times {{10}^{9}}\] years done
clear
B) \[45.3\times {{10}^{10}}\] years done
clear
C) \[4.53\times {{10}^{9}}\] years done
clear
D) \[4.53\times {{10}^{10}}\] years done
clear
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question_answer13) Halflife of radium is 1580 yrs. Its average life will be [AIIMS 1999; AFMC 1999; CPMT 1999]
A) \[2.5\times {{10}^{3}}yrs\] done
clear
B) \[1.832\times {{10}^{3}}yrs\] done
clear
C) \[2.275\times {{10}^{3}}yrs\] done
clear
D) \[8.825\times {{10}^{2}}yrs\] done
clear
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question_answer14) 8 gms of a radioactive substance is reduced to \[0.5\,g\] after 1 hour. The \[{{t}_{1/2}}\] of the radioactive substance is [DCE 2000]
A) 15 min done
clear
B) 30 min done
clear
C) 45 min done
clear
D) 10 min done
clear
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question_answer15) 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 done
clear
B) 7.5 hours done
clear
C) 10 hours done
clear
D) 20 hours done
clear
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question_answer16) Number of aparticles emitted per second by a radioactive element falls to 1/32 of its original value in 50 days. The halflifeperiod of this elements is [AMU 2001]
A) 5 days done
clear
B) 15 days done
clear
C) 10 days done
clear
D) 20 days done
clear
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question_answer17) What is the halflife of a radioactive substance if 87.5% of any given amount of the substance disintegrates in 40 minutes [Kerala CET 1996]
A) 160 min done
clear
B) 10 min done
clear
C) 20 min done
clear
D) 13 min 20 sec done
clear
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question_answer18) A radioactive isotope has a \[{{t}_{1/2}}\] of 10 days. If today 125 gm of it is left, what was its weight 40 days earlier [EAMCET 1991]
A) \[600gm\] done
clear
B) \[1000gm\] done
clear
C) \[1250gm\] done
clear
D) \[2000gm\] done
clear
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question_answer19) The halflife of \[_{6}{{C}^{14}}\], if its decay constant is \[6.31\times {{10}^{4}}\] is [CBSE PMT 2001]
A) 1098 yrs done
clear
B) 109.8 yrs done
clear
C) 10.98 yrs done
clear
D) 1.098 yrs done
clear
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question_answer20) A radioactive sample has a halflife of 1500 years.A sealed tube containing \[1gm\] of the sample will contain after 3000 years [MNR 1994; UPSEAT 2001, 02]
A) \[1gm\] of the sample done
clear
B) \[0.5gm\] of the sample done
clear
C) \[0.25gm\] of the sample done
clear
D) \[0.00gm\] of the sample done
clear
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question_answer21) The halflife 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 done
clear
B) 8.0 g done
clear
C) 12.0 g done
clear
D) 16.0 g done
clear
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question_answer22) \[\frac{15}{16}th\] of a radioactive sample decays in 40 days halflife of the sample is [DCE 2001]
A) 100 days done
clear
B) 10 days done
clear
C) 1 day done
clear
D) \[{{\log }_{e}}\]2 days done
clear
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question_answer23) A radioactive element with halflife 6.5 hrs has \[48\times {{10}^{19}}\]atoms. Number of atoms left after 26 hrs [BHU 2003]
A) \[24\times {{10}^{19}}\] done
clear
B) \[12\times {{10}^{19}}\] done
clear
C) \[3\times {{10}^{19}}\] done
clear
D) \[6\times {{10}^{19}}\] done
clear
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question_answer24) The halflife 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 done
clear
B) 156 hours done
clear
C) 20.9 hours done
clear
D) 2.09 hours done
clear
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question_answer25) The halflife 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 done
clear
B) 560 days done
clear
C) 280 days done
clear
D) 420 days done
clear
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question_answer26) Percentage of a radioactive element decayed after 20 sec when halflife is 4 sec [BHU 2003]
A) 92.25 done
clear
B) 96.87 done
clear
C) 50 done
clear
D) 75 done
clear
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question_answer27) Consider an aparticle just in contact with a \[_{92}{{U}^{238}}\]nucleus. Calculate the coulombic repulsion energy (i.e. the height of the coulombic barrier between \[{{U}_{238}}\] and alpha particle) assuming that the distance between them is equal to the sum of their radii [UPSEAT 2001]
A) 23.8517x\[{{10}^{4}}eV\] done
clear
B) \[26.147738\times \text{1}{{\text{0}}^{\text{4}}}eV\] done
clear
C) \[\text{25}\text{.3522}\times {{10}^{4}}eV\] done
clear
D) \[20.2254\times {{10}^{4}}eV\] done
clear
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question_answer28) The halflife period of \[P{{b}^{210}}\] is 22 years. If 2 gm of \[P{{b}^{210}}\] is taken, then after 11 years how much of \[P{{b}^{210}}\] will be left [KCET 2001]
A) 1.414 gm done
clear
B) 2.428 gm done
clear
C) 3.442 gm done
clear
D) 4.456 gm done
clear
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question_answer29) A wood specimen from an archeological centre shows a \[_{6}^{14}C\] activity of 5.0 counts/min/gm of carbon. What is the age of the specimen \[({{t}_{1/2}}\]for \[_{6}^{14}C\] is 5000 years) and a freshly cut wood gives 15 counts/min/gm of carbon [AMU (Engg.) 2002]
A) \[5.78\times {{10}^{4}}\]years done
clear
B) \[9.85\times {{10}^{4}}\]years done
clear
C) \[7.85\times {{10}^{3}}\]years done
clear
D) \[0.85\times {{10}^{4}}\]years done
clear
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question_answer30) \[_{92}{{U}^{235}}+n\to \]fission product+neutron\[+3.20\times {{10}^{11}}J\]. The energy released when \[1g\] of \[_{92}{{U}^{235}}\] undergoes fission is [CBSE PMT 1997]
A) \[12.75\times {{10}^{8}}kJ\] done
clear
B) \[18.60\times {{10}^{9}}kJ\] done
clear
C) \[8.21\times {{10}^{7}}kJ\] done
clear
D) \[6.55\times {{10}^{6}}kJ\] done
clear
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question_answer31) The triad of nuclei that is isotonic is [IIT 1988; DCE 2000;MP PMT 2004]
A) \[_{6}{{C}^{14}},{{\,}_{7}}{{N}^{15}},{{\,}_{9}}{{F}^{17}}\] done
clear
B) \[_{6}{{C}^{12}},{{\,}_{7}}{{N}^{14}},{{\,}_{9}}{{F}^{19}}\] done
clear
C) \[_{6}{{C}^{14}},{{\,}_{7}}{{N}^{14}},{{\,}_{9}}{{F}^{17}}\] done
clear
D) \[_{6}{{C}^{14}},{{\,}_{7}}{{N}^{14}}{{,}_{9}}{{F}^{19}}\] done
clear
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question_answer32) 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 done
clear
B) 85.5 done
clear
C) 40.0 done
clear
D) 86.0 done
clear
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