Nuclei -Important Questions & Preparation Tips

In this article you will get the clue that from where and how the questions are being framed from chapter Nuclei

Created On: Oct 7, 2013 11:48 IST
Modified On: Mar 15, 2016 15:47 IST

CBSE Class 12th Chapter, Nuclei comes under the topic Atoms & Nuclei which carries 6 Marks in board exam. Experts of offer the best practice material that covers all important questions so that students will not miss any portion while preparing for board exams or competitive exams. Consider the mentioned terms/questions at the time of studying.

  • Define 1a.m.u? What is its relation with kilogram?
  • Differentiate between isotones and isobars?
  • If the radius of the earth is given 6,371 km. What would be the mass of earth?

          (Given: R0 = 1.2 x 10--15)

  • Calculate the energy contained in 1kg of potatoes?
  • Define mass defect and binding energy of nucleus? With binding energy curve in mind, show that why is uranium so unstable?
  • What do you mean by the saturation property of nuclear forces?

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  • What do you understand by the term fission and fusion?
  • The activity of a radioactive material drops to 1/14 th of its value in 24 hours. Calculate the half-life and the decay constant?
  • Is the mass electrons obtained by all sources equal?
  • The mass of β-particle is higher than the mass of electrons obtained by other sources, whereas β-particles are also electrons.  Why?

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  • What do you mean by the half life of a radioactive element? Explain half life time and decay constant by drawing a curve between undisintegrated atoms of the element and time?
  • After a certain apse of time, the fraction of radioactive polonium undecayed is found to be 4.625% of its initial quantity. What is the duration of this time lapse if the half life of polonium is 138 days?
  • How can you show that the nuclear force is very much stronger than Coulomb force?
  • What are the types of nuclear decay occurring in nature?
  • What is activity of a radioactive simple? How can you account for the exponential decay of a radioactive species?

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  • Differentiate between the units Becquerel and curie?
  • Explain how radioactive elements can emit β-particles even though atomic nuclei do not contain these particles. Hence explain why the mass number of a radioactive nuclide does not change during β-decay?
  • A radioactive sample is kept at the centre of a large evacuated sphere. How safe will it be?
  • Why is the mass of nucleus always less than the sum of the masses of its constituents, neutrons and protons?
  • Name the radiation which when becomes neutral, becomes the atom of a rare gas?
  • Draw a graph showing the variation of potential energy of a pair of nucleons as a pair of nucleons as a function of their separation. Indicate the regions in which the nuclear force is attractive and repulsive?

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  • Prove that the instantaneous rate of change of the activity of a radioactive substance is inversely proportional to the square of its half life?
  • If the total number of protons and neutrons in a nuclear reaction is conserved, how then is the energy absorbed or evolved in the reaction? Explain.
  • State the law of radioactive decay. If N0is the number of radioactive nuclei in the sample at some initial time t0, find out the relation to determine the number N present at a subsequent time. Draw a plot of N as a function of time?
  • The half life of a given radioactive nuclide is 1338.6 days. What is the mean life of this nuclide? After how much time will a given sample of this radioactive nuclide get reduced to only 12.5% of its initial value?
  • A star converts all its hydrogen to helium achieving 100% helium composition. It then converts helium to carbon via the reaction:

                        324He → 212C + 7.27 MeV

          The mass of the star is 5.0 x 1030 kg and it generates energy at the rate of 5 x 1030 watt. How long will it take to convert all its helium to carbon?

  • The half life of 612C is 5700 years. What does it mean? Two radioactive nuclei P and Q initially contain an equal number of atoms. Their half life is 1 hour and 2 hours respectively. Calculate the ratio of their rates of disintegration after two hours?

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