Sample QuestionsNuclei questions
One sample from each question group in this chapter. Select any group above to see the full set with answer keys.
Fusion reactions take lace at high temperature because:
- A
Atoms are ionized at high temperature.
- B
Molecules break up at high temperature.
- C
Nuclei break up at high temperature.
- ✓
Kinetic energy is high enough to overcome repulsion between nuclei.
Answer: D.
View full solution →Which of the following statement best describe Nuclear fusion reaction ?
- ✓
Two smaller nuclei are combined into a more massive nuclei.
- B
The electrons are exchanged from one or more substances to produce a different substance, and the elements are the same in the products and reactants.
- C
The nucleus of a large atom is split into two or more fragments.
- D
Answer: A.
View full solution →Which one of the following properties of an element is not variable?
Answer: B.
View full solution →An $\alpha$-particle captures an electron. What does it change to?
- A
$He^{2+}$
- B
$He$
- ✓
$He^+$
- D
$\alpha$
Answer: C.
View full solution →In $\gamma\ \text{ray}$ emission from a nucleus:
- A
Only the proton number changes.
- B
Both the neutron number and the proton number change.
- ✓
There is no change in the proton number and the neutron number.
- D
Only the neutron number changes.
Answer: C.
View full solution →For question, statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a) (b) (c) and (d) as given below.
- Both A and R are true, and R is the correct explanation of A.
- Both A and R are true, but R is NOT the correct explanation of A.
- A is true, but R is false.
- A is false and R is also false.
Assertion (A): $_7^{14}\text{N}$ is stable.
Reason (R): Nuclei having an odd number of protons and an odd number of neutrons are generally less stable than the one having even number of protons and even number of neutrons. View full solution →For question, statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a) (b) (c) and (d) as given below.
- Both A and R are true, and R is the correct explanation of A.
- Both A and R are true, but R is NOT the correct explanation of A.
- A is true, but R is false.
- A is false and R is also false.
Assertion (A): Density of all the nuclei is same.
Reason (R): Radius of nucleus is directly proportional to the cube root of mass number.
For question, statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a) (b) (c) and (d) as given below.
- Both A and R are true, and R is the correct explanation of A.
- Both A and R are true, but R is NOT the correct explanation of A.
- A is true, but R is false.
- A is false and R is also false.
Assertion (A): Energy is released in a nuclear reaction.
Reason (R): In any nuclear reaction the reactants and resultant products obey the law of conservation of charge and mass only.
For question, statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a) (b) (c) and (d) as given below.
- Both A and R are true, and R is the correct explanation of A.
- Both A and R are true, but R is NOT the correct explanation of A.
- A is true, but R is false.
- A is false and R is also false.
Assertion (A): Cadmium rods, used in a nuclear reactor, control the rate of fission.
Reason (R): Cadmium rods, used in a nuclear reactor, control the rate of fission.
For question, statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a) (b) (c) and (d) as given below.
- Both A and R are true, and R is the correct explanation of A.
- Both A and R are true, but R is NOT the correct explanation of A.
- A is true, but R is false.
- A is false and R is also false.
Assertion (A): A fission reaction can be more easily controlled than a fission reaction.
Reason (R): The percentage of mass converted to energy in a fission reaction is 0.1% whereas in a fission reaction it is 0.4%
Why is it found experimentally difficult to detect neutrinos in nuclear $\beta$-decay?
View full solution →Define the activity of a given radioactive substance. Write its S.I. unit.
Write any two characteristic properties of nuclear force.
Two nuclei have mass numbers in the ratio 1 : 8. What is the ratio of their nuclear radii?
State two characteristic properties of nuclear force.
The three stable isotopes of neon: $^{20}_{10}\text{Ne},\ ^{21}_{10}\text{Ne }\text{ and }\ ^{22}_{10}\text{Ne}$ have respective abundances of 90.51%, 0.27% and 9.22%. The atomic masses of the three isotopes are 19.99 u, 20.99 u and 21.99 u, respectively. Obtain the average atomic mass of neon.
View full solution →Suppose, we think of fission of a $^{56}_{26}\text{Fe}$ nucleus into two equal fragments, $^{28}_{13}\text{Al}.$ Is the fission energetically possible? Argue by working out Q of the process. Given $\text{m}(^{56}_{26}\text{Fe})=55.93494\text{ u and m }(^{28}_{13}\text{Al})=27.98191\text{ u}.$
View full solution →The half-life of $^{90}_{38}\text{Sr}$ is 28 years. What is the disintegration rate of 15 mg of this isotope?
View full solution →Two stable isotopes of lithium $^6_3\text{Li }\text{ and }\ ^7_3\text{Li}$ have respective abundances of 7.5% and 92.5%. These isotopes have masses 6.01512 u and 7.01600 u, respectively. Find the atomic mass of lithium.
View full solution →Find the condition under which the charged particles moving with different speeds in the presence of electric and magnetic field vectors can be used to select charged particles of a particular speed.
The normal activity of living carbon-containing matter is found to be about 15 decays per minute for every gram of carbon. This activity arises from the small proportion of radioactive $ ^{14}_6\text{C}$ present with the stable carbon isotope $^{12}_6\text{C}.$ When the organism is dead, its interaction with the atmosphere (which maintains the above equilibrium activity) ceases and its activity begins to drop. From the known half-life (5730 years) of $^{14}_6\text{C },$ and the measured activity, the age of the specimen can be approximately estimated. This is the principle of $^{14}_6\text{C}$ datingused in archaeology. Suppose a specimen from Mohenjodaro gives an activity of 9 decays per minute per gram of carbon. Estimate the approximate age of the Indus-Valley civilisation.
View full solution →The radionuclide $^{11}C$ decays according to
$^{11}_{6}\text{C}\rightarrow^{11}_{5}\text{B}+\text{e}^{+}+\text{v}:\ \text{T}_{1/2}=20.3 \text{ min}$
The maximum energy of the emitted positron is 0.960 MeV.
Given the mass values:
$\text{m}(^{11}_{6})=10=11.011434\text{ u and m}(^{11}_{6}\text{B})=11.009305\text {u}.$
calculate Q and compare it with the maximum energy of the positron emitted.
View full solution →In a periodic table the average atomic mass of magnesium is given as 24.312 u. The average value is based on their relative natural abundance on earth. The three isotopes and their masses are $^{24}_{12}\text{Mg }23.98504\text{u}),^{25}_{12}\text{Mg }(24.98584\text{u})\text{ and }^{26}_{12}\text{Mg }(25.98259\text{u}).$ The natural abundance of $^{24}_{12}\text{Mg}\text{ is }78.99\%$ by mass. Calculate the abundances of other two isotopes.
View full solution →Boron has two stable isotopes, $^{10}_5\text{B }\text{ and }\ ^{11}_5\text{B}.$ Their respective masses are 10.01294 u and 11.00931 u, and the atomic mass of boron is 10.811 u. Find the abundances of $^{10}_5\text{B }\text{ and }\ ^{11}_5\text{B}.$
View full solution →A 1000 MW fission reactor consumes half of its fuel in 5.00 y. How much $^{235}_{92}\text{U}$ did it contain initially? Assume that the reactor operates 80% of the time, that all the energy generated arises from the fission of $^{235}_{92}\text{U}$ and that this nuclide is consumed only by the fission process.
View full solution →The neutron separation energy is defined as the energy required to remove a neutron from the nucleus. Obtain the neutron separation energies of the nuclei $^{41}_{20}\text{Ca }\text{ and }^{27}_{13}\text{Al}$ from the following data:
$\text{m}(^{40}_{20}\text{Ca})=39.962591\text{ u}$
$\text{m}(^{41}_{20}\text{Ca})=40.962278\text{ u}$
$\text{m}(^{26}_{13}\text{Al})=25.986895\text{ u}$
$\text{m}(^{27}_{13}\text{Al})=26.981514\text{ u}$
View full solution →Obtain the amount of $^{60}_{27}\text{Co}$ necessary to provide a radioactive source of 8.0 mCi strength. The half-life of $^{60}_{27}\text{Co}$ is 5.3 years.
View full solution →Under certain circumstances, a nucleus can decay by emitting a particle more massive than an $\alpha$particle. Consider the following decay processes:
$^{223}_{88}\text{Ra}\rightarrow^{209}_{82}\text{Pb}+^{14}_{6}\text{C}$
$^{223}_{88}\text{Ra}\rightarrow^{219}_{86}\text{Rn}+^{4}_{2}\text{He}$
Calculate the Q-values for these decays and determine that both are energetically allowed.
View full solution →A radioactive isotope has a half-life of T years. How long will it take the activity to reduce to
- 3.125%,
- 1% of its original value?
Consider the fission of $^{238}_{92}\text{U}$ by fast neutrons. In one fission event, no neutrons are emitted and the final end products, after the beta decay of the primary fragments, are $^{140}_{58}\text{Ce}$ and $^{99}_{44}\text{Ru}.$ Calculate Q for this fission process.
The relevant atomic and particle masses are:
$\text{m}(^{238}_{92}\text{U})=238.05079\text{ u}$
$\text{m}(^{140}_{58}\text{Ce})=139.90543\text{ u}$
$\text{m}(^{99}_{44}\text{Ru})=98.90594\text{ u}$
View full solution →For the past some time, Aarti had been observing some erratic body movement, unsteadiness and lack of coordination in the activities of her sister Radha, who also used to complain of severe headache occasionally. Aarti suggested to her parents to get a medical check-up of Radha. The doctor thoroughly examined Radha and diagnosed that she has a brain tumour.
- What, according to you, are the values displayed by Aarti?
- How can radioisotopes help a doctor to diagnose brain tumour?
For the past some time, Aarti had been observing some erratic body movement, unsteadiness and lack of coordination in the activities of her sister Radha, who also used to complain of severe headache occasionally. Aarti suggested to her parents to get a medical check-up of Radha. The doctor thoroughly examined Radha and diagnosed that she has a brain tumour.
- What, according to you, are the values displayed by Aarti?
- How can radioisotopes help a doctor to diagnose brain tumour?
Why is it found experimentally difficult to detect neutrinos in nuclear $\beta$-decay?
View full solution →For the past some time, Aarti had been observing some erratic body movement, unsteadiness and lack of coordination in the activities of her sister Radha, who also used to complain of severe headache occasionally. Aarti suggested to her parents to get a medical check-up of Radha. The doctor thoroughly examined Radha and diagnosed that she has a brain tumour.
- What, according to you, are the values displayed by Aarti?
- How can radioisotopes help a doctor to diagnose brain tumour?
In pair annihilation, an electron and a positron destroy each other to produce gamma radiation. How is the momentum conserved?