NUCLEAR CHEMISTRY (for UPSC, CSIR-NET(JRF), SET, BARC etc Exams )

MULTIPLE CHOICE QUESTIONS:

1. Which one of the following types of particles is the MOST highly penetrating to biological tissues?

    a. Alpha particles.

    b. Beta particles.

    c. Positrons.

    d. Electrons

Ans. Electrons.

2. Americium- 241 is the radioactive isotope that is used in smoke detectors. Americium-241 undergoes

    alpha decay with a half-life of 458 years. What is the product nuclide that is produced when

    americium-241 radioactively decays?

   a. Neptunium-237

   b. Curium-241

   c. Plutonium-241

   d. Americium-240 

   e. Plutonium-240

Ans. Neptunium-237.

3. Positron emission tomography (PET) scans are used medicinally to diagnose certain biological

   disorders. The most common radioactive isotope used in this procedure is fluorine-18, which is

   a positron emitter. In a PET scan, which one of the following species is actually measured in

   order to create a three-dimensional image of the afflicted organ?

   a. alpha particles

   b. beta particles

   c. gamma rays 

   d. positrons

   e. neutrons

Ans. gamma rays

4. In lecture, you observed a desiccator that was used for many years to store radioactive radium compounds. What color was the desiccator?

    a. yellow

    b. orange

    c. purple

    d. green

    e. black

Ans. Purple.

5. The radioactive nuclide, iodine-131, is used medicinally as a radiotracer for the diagnosis and

    treatment of illnesses associated with the thyroid gland. If the rate constant for decay of

    iodine-131 is 9.9 x 10^-7 s^-1, calculate the half-life (in s) of iodine-131.

Ans. 7x 10^-7

6. Calculate the binding energy per nucleon in millions of electron volts (MeV) for nitrogen-15.

    The atomic mass of nitrogen-15 is 15.00011 amu. 

Ans. 7.7

7. What is the final, stable nuclide, X, if radon-222 decays by the emission of four alpha particles

    and four beta particles?

    a. tungsten-206 

    b. tungsten-214

    c. platinum-202

    d. platinum-210

    e. lead-206

Ans.  Lead-206

8. An archeologist unearths a bone sample and wants to know the age of the bone. Her chemist

    friend determines that 41.7% of the initial amount of carbon-14 in the bone sample has

    decayed. If the half-life of carbon-14 is 5730 years, the age of the bone is:

    a. 4460 years

    b. 5730 years

    c. 7230 years

    d. 10200 years

    e. 11460 years.

Ans.  4460 years.

9. Which of the following characteristics is/are important considerations for radiotracers that will

    be used for diagnosing illness in the body?

    a. The radiotracer should have a short half-life.

    b. The radiotracer should localize in a certain part of the body.

    c. The radiotracer should produce radiation that can be detected externally.

    d. (a) and (b). 

    e. (a), (b) and (c). 

Ans. (a), (b) & (c)

10. When a nuclide is assembled from its constituent protons, neutrons, and electrons, there is

     about a 1% decrease in mass. When a chemical compound is similarly made from its

     constituent elements there is no discernible change in mass. The best reason for this

     difference is that:

     a. chemical reactions are intrinsically different from nuclear reactions. 

     b. the formation of a nuclide from its constituents is always exothermic whereas the formation

        of a compound from the elements can be either exothermic or endothermic.  

     c. Einstein's equation, E = mc², applies to nuclei but not to molecules.

     d. chemical reactions release far less energy than nuclear reactions and so the mass change

         is too small to observe.

     e. mass is conserved in chemical reactions but is not conserved in nuclear reactions. 

Ans. d. chemical reactions release far less energy than nuclear reactions and so the mass

          change is too small to observe.

11. The mass of chlorine-37 is 36.96590 amu. The binding energy per nucleon of chlorine-37 is: 

     a. -1.41 x 10^-12 J/nucleon

     b.  1.29 x 10^-12 J/nucleon

     c.  1.37 x 10^-12 J/nucleon

     d.  5.08 x 10^-11 J/nucleon

     e.  5.08 x 10^-8 J/nucleon

Ans.  c.  1.37 x 10^-12 J/nucleon

12. The only stable nuclide with A = 35 is chlorine-35. Which of the following equations correctly

     describe the process by which phosphorus-35 decays to chlorine-35?

     a. phosphorus-35 -> chlorine-35 + beta particle

     b. phosphorus-35 -> sulfur-35 + beta particle
         sulfur-35 -> chlorine-35 + beta particle

     c. phosphorus-35 -> silicon-35 + beta particle
         silicon-35 -> chlorine-35 + beta particle

     d. phosphorus-35 -> chlorine-35 + positron

     e. phosphorus-35 + e- -> sulfur-35
         sulfur-35 + e- -> chlorine-35

Ans.   b. phosphorus-35 -> sulfur-35 + beta particle
             sulfur-35 -> chlorine-35 + beta particle

13. A freshly prepared sample of yttrium-90 undergoes 7.6 x 10⁵ disintegrations per minute (dpm) at a certain time. Exactly

      14 days later, the same sample undergoes 1.6 x 10⁴  dpm. The half- life of yttrium-90 is: 

     a. 0.20 day

     b. 2.5 day

     c. 2.7 day

     d. 3.8 day

     e. 14 day

Ans.     b. 2.5 day

14. What is the product nuclide of the decay of thorium-232? Thorium-232 has a half-life of 1.4 x 10¹⁰ years and

      radioactively decays by alpha emission.

     a. radon-230

     b. radium-228

     c. actinium-232

     d. proactinium-232

     e. uranium-235.

Ans.   b. radium-228