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Nuclei · Question 3

RE-NEET (UG) 2026MCQEasy📈 Topic in 50% papers+4−1
1

Consider the following nuclear reaction 238U 234Th + 4He Take masses of 238U, 234Th and 4He as 238.050 u, 234.043 u and 4.003 u, respectively. The Q value for the reaction, in keV, is: [Given: 1 u = 931.5 MeV c-2]

  1. 3740
  2. 3726
  3. 3730
  4. 3736

Answer

(2) 3726

Solution

The mass defect of the reaction is:

m = m( 238U) - [m( 234Th) + m(4He)]

m = 238.050 - (234.043 + 4.003) = 238.050 - 238.046 = 0.004 u

The Q value is:

Q = m 931.5 MeV = 0.004 931.5 MeV = 3.726 MeV = 3726 keV

Answer: (2)

RE-NEET (UG) 2026

Keep practising — Nuclei

2

29082X Y e+ Z - P e- Q In the nuclear emission stated above, the mass number and atomic number of the product Q respectively, are

  1. 280, 81
  2. 286, 80
  3. 288, 82
  4. 286, 81
NEET (UG) 2024
3

Water is used as a coolant in a nuclear reactor because of its

  1. high thermal expansion coefficient
  2. high specific heat capacity
  3. low density
  4. low boiling point
RE-NEET (UG) 2024
4

Select the correct statements among the following : Choose the most appropriate answer from the options given below :

  1. A, B and C only
  2. A, B and D only
  3. A and B only
  4. C and D only
RE-NEET (UG) 2024
5

The half life of a radioactive substance is 20 minutes. In how much time, the activity of substance drops to ( 116 )th of its initial value?

  1. 40 minutes
  2. 60 minutes
  3. 80 minutes
  4. 20 minutes
Out of syllabusNEET (UG) 2023
6

A nucleus of mass number 189 splits into two nuclei having mass number 125 and 64. The ratio of radius of two daughter nuclei respectively is

  1. 1 : 1
  2. 4 : 5
  3. 5 : 4
  4. 25 : 16
NEET (UG) 2022
7

In the given nuclear reaction, the element X is 2211Na X + e+ +

  1. 2311Na
  2. 2310Ne
  3. 2210Ne
  4. 2212Mg
Out of syllabusNEET (UG) 2022
8

Given below are two statements In the light of the above statements, choose the most appropriate answer from the options given below :

  1. Statement I is incorrect but statement II is correct
  2. Both statement I and statement II are correct
  3. Both statement I and statement II are incorrect
  4. Statement I is correct but statement II is incorrect
Out of syllabusNEET (UG) 2022 (Phase 2)
9

At any instant, two elements X1 and X2 have same number of radioactive atoms. If the decay constant of X1 and X2 are 10 and respectively, then the time when the ratio of their atoms becomes 1e respectively will be :

  1. 15
  2. 111
  3. 19
  4. 16
Out of syllabusNEET (UG) 2022 (Phase 2)
10

A nucleus with mass number 240 breaks into two fragments each of mass number 120, the binding energy per nucleon of unfragmented nuclei is 7.6 MeV while that of fragments is 8.5 MeV. The total gain in the Binding Energy in the process is :

  1. 216 MeV
  2. 0.9 MeV
  3. 9.4 MeV
  4. 804 MeV
NEET (UG) 2021
11

The half life of a radioactive nuclide is 100 hours. The fraction of original activity that will remain after 150 hours would be :

  1. 23 2
  2. 12
  3. 12 2
  4. 23
Out of syllabusNEET (UG) 2021

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