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NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12 PDF Download

2024

Q1: NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
In the nuclear emission stated above, the mass number and atomic number of the product Q respectively, are
(a) 280, 81
(b) 286, 80
(c) 288, 82
(d) 286, 81          
Ans:
(d) 286, 81 
To determine the mass number and atomic number of the final product Q in the provided nuclear reactions, we need to analyze the impact of each type of decay (alpha, positron emission, beta-minus decay, and electron capture) on the mass number and atomic number of the initial element NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
1. Alpha decay (α decay): In alpha decay, an alpha particle (which is a NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12 nucleus) is emitted. This reduces the mass number by 4 units and the atomic number by 2 units.
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
2. Beta plus decay (positron emission, e+): During positron emission, a proton in the nucleus is transformed into a neutron, and a positron is emitted. This decreases the atomic number by 1 but does not change the mass number.
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
3. Beta-minus decay (β decay): In a beta-minus decay, a neutron in the nucleus converts into a proton and an electron (beta particle) and an antineutrino are emitted. This results in an increase in the atomic number by 1, while the mass number remains unchanged.
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
4. Electron capture (e capture): During electron capture, an atomic electron is absorbed by the nucleus, causing a proton to convert into a neutron. This process decreases the atomic number by 1 without altering the mass number.
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
From the calculations above, the mass number of Q is 286, and its atomic number is 79. Comparing these values with the multiple choices:
Option A: Mass number = 280, Atomic number = 81
Option B: Mass number = 286, Atomic number = 80
Option C: Mass number = 288, Atomic number = 82
Option D: Mass number = 286, Atomic number = 81
None of these match exactly, implying an error in the problem or the answer options. Based on the correct atomic number calculations and assuming option D is meant to be atomic number 79, then the corrected choice would have been:
D: Mass number = 286, Atomic number = 79

2023

Q.1. The half life of a radioactive substance is 20 minutes. In how much time, the activity of substance drops to  (1/16)th of its initial value?      
(a) 20 minutes
(b) 40 minutes
(c) 60 minutes
(d) 80 minutes
Ans:
(d) 80 minutes
Solution: 
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12

2022

Q.2. In the given nuclear reaction, the element X is     

NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
(a) NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
(b) NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12

 (c) NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12

(d)  NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12

Ans: (b) NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
Solution: 
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12

2021

Q.3. A nucleus with mass number 240 breaks into 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:   
(a)  804 MeV 
(b) 216 MeV 
(c) 0.9 MeV 
(d) 9.4 MeV
Ans: 
(b) 216 MeV
Solution:

NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
Given binding energy per nucleon of X, Y & Z are 7.6 MeV, 8.5 MeV & 8.5 MeV respectively.
Gain in binding energy is :-
Q = Binding Energy of products – Binding energy of reactants
= (120 × 8.5 × 2) – (240 × 7.6) MeV
= 216 MeV

Q.4. A radioactive nucleus NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12 undergoes spontaneous decay in the sequence
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
Where Z is the atomic number of element X. The possible decay particles in the sequence are :     
 (a)  β+,α,β-
(b) β-,α,β+

 (c)  α,β-+
(d) α,β+-
Ans:
(a)  β+,α,β-
Solution:

NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12β+ decreases atomic number by 1
α decreases atomic number by 2
β- decreases atomic number by 1

Q.5. The half-life of a radioactive nuclide is 100 hours. The fraction of original activity that will remain after 150 hours would be:   
(a) 2/3
(b)  2/3√2 
(c) 1/2
(d)  1/2√2

Ans: (d)  1/2√2
Solution:

NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12

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2020

Q.6. The energy equivalent of 0.5 g of a substance is :    
(a) 1.5×1013 J
(b) 0.5×1013J
(c) 4.5×1016J
(d) 4.5×1013J

Ans: (d)  4.5×1013J
Solution:
E = Δmc2 = 0.5 × 10-3 × (3 × 108)2
= 0.5 ×10-3 × 9 ×1016
E = 4.5 ×1013 J

Q.7. When a uranium isotopeNEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12is bombarded with a neutron, it generates NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12three neutrons and : 
(a) 
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
(b)
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
(c)
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
(d)
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12

Ans: (c) NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
Solution: 
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
92 = 36 + Z; ← A + 89 + 3 = 235 ⇒ A = 144
Z = 56

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2019

Q.8. 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:   
(a) 20
(b) 10
(c) 30
(d) 15
Ans: (a) 
20
Solution:
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12

2017

Q.9. Radioactive material 'A' has decay constant '8 λ' and material 'B' has decay constant 'λ'. Initially they have same number of nuclei. After what time, the ratio of number of nuclei of material 'B' to that 'A' will be 1/e?  
(a)  1/7λ
(b)  1/8λ
(c) 1/9λ
(d) 1/10λ
Ans: (a)  
1/7λ
Solution:

NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12

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2014

Q.10. The Binding energy per nucleon of NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12 nuclei are 5.60 MeV and 7.06 MeV, respectively. In the nuclear reaction NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12 the value of energy Q released is : 
(a)  8.4 MeV
(b)  17.3 MeV
(c)  19.6 MeV
(d) −2.4 MeV
Ans: (b) 
17.3 MeV
Solution:

NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12

Q.11. A radio isotope ‘X’ with a half life 1.4 × 109 years decays to ‘Y’ which is stable. A sample of the rock from a cave was found to contain ‘X’ and ‘Y’ in the ratio 1 : 7. The age of the rock is 
(a) 4.20 × 109 years
(b) 8.40 × 109 years
(c) 1.96 × 109 years
(d) 3.92 × 109 years
Ans: (a) 
4.20 × 109 years
Solution:

Ratio of X:Y is given = 1:7
That is,
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
⇒ 7mx = my
Let, the initial total mass is m.
NEET Previous Year Questions (2014-2024): Nuclei | Physics Class 12
Therefore, time taken to become 1/8 unstable part
= 3 x T1/2
= 3 x 1.4 x 109
= 4.2 x 109 y

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FAQs on NEET Previous Year Questions (2014-2024): Nuclei - Physics Class 12

1. What is the significance of nuclear reactions in NEET exam preparation?
2. How can I effectively study for the Nuclei chapter for NEET?
Ans.Effective study methods include reviewing NCERT textbooks, practicing previous year NEET questions, and solving numerical problems related to nuclear physics. Additionally, creating summary notes and focusing on key concepts like binding energy and radioactive decay can be beneficial.
3. What types of questions related to Nuclei can I expect in the NEET exam?
Ans.Questions may include topics like the calculation of binding energy, understanding decay processes, and applications of nuclear reactions. Conceptual questions may also ask for explanations of phenomena like fission and fusion.
4. How important is the concept of binding energy in NEET exams?
Ans.Binding energy is crucial as it helps in understanding the stability of nuclei. It frequently appears in questions related to nuclear stability, decay, and energy release in fission and fusion processes, making it an important topic for NEET preparation.
5. Are there any common mistakes to avoid when studying the Nuclei chapter for NEET?
Ans.Common mistakes include neglecting the mathematical aspects of nuclear physics, not practicing enough numerical problems, and underestimating the importance of definitions and fundamental concepts. It's crucial to thoroughly understand each topic and practice consistently.
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