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Nuclei · Question 7

NEET (UG) 2023MCQEasy📈 Topic in 25% papers+4−1
1

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

Answer

(3) 80 minutes

Solution

AA0 = ( 12 )n = 116

n = 4 half-lives

t = n T1/2 = 4 20 = 80 minutes

Answer: (3)

Out of syllabusNEET (UG) 2023

Keep practising — Nuclei

2

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
3

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
4

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)
5

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)
6

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
7

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
8

A radioactive nucleus ZAX Z-1B Z-3C Z-2D, where Z is the atomic number of element X. The possible decay particles in the sequence are :

  1. -, , +
  2. , -, +
  3. , +, -
  4. +, , -
Out of syllabusNEET (UG) 2021
9

The energy equivalent of 0.5 g of a substance is :

  1. 4.5 1013 J
  2. 1.5 1013 J
  3. 0.5 1013 J
  4. 4.5 1016 J
NEET (UG) 2020
10

When a uranium isotope 23592U is bombarded with a neutron, it generates 8936Kr, three neutrons and :

  1. 9140Zr
  2. 10136Kr
  3. 10336Kr
  4. 14456Ba
Out of syllabusNEET (UG) 2020
11

For a radioactive material, half-life is 10 minutes. If initially there are 600 number of nuclei, the time taken (in minutes) for the disintegration of 450 nuclei is

  1. 20
  2. 10
  3. 30
  4. 15
Out of syllabusNEET 2018

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