Inside the Sun the fusion of hydrogen atoms to form helium is the main source of the Sun’s energy. One such reaction involves the fusion of two deuterium to produce one isotope of helium with mass number 3 along with the release of one neutron.Write out the equation that represents this reaction and calculate the energy released during this reaction, in electronvolts.
(Speed of light 3 108 m s1; mass of hydrogen-2 nucleus 3.342 1027 kg; mass of helium-3 nucleus 5.007 1027 kg; mass of neutron 1.674 1027 kg.)
SAMPLE ANSWER 22C The equation that represents this reaction is:
2 1H 2
1H :3 2He 1 0n
mass of reactants 2 (3.342 1027) 6.684 1027 kg mass of products (5.007 1027) (1.674 1027) 6.681 1027 kg mass defect 3.0 1030 kg Using mass-energy equivalence equation: E mc2 (3.0 1030)(3 108)2 2.7 1013 J E (J) E (eV) 1.6 1019
The energy released is 1.7 MeV. QE (eV) 2.7 1013
1.6 1019 1.69 106 ev
EXERCISE 22.2 NUCLEAR ENERGY
Refer to the Periodic Table on p. 495 when answering these questions.Take the speed of light as 2.998 108 m s1 in all these questions. Q1 100 MJ of energy are released in a nuclear reaction. Calculate the loss of mass during the reaction.
Q2 Calculate the energy released when uranium-238 decays into thorium-234 with the emission of an alpha particle, given that the loss in mass is 7.58 1030 kg.
Q3 Examples of the fission of uranium-235 are: (i) barium-141 and krypton-92 (ii) caesium-140 and rubidium-93.
Write the equations that represent each of the reactions.
Q4 In fusion reactions that take place in the Sun, two isotopes of hydrogen, one with a mass number of 1, the other with a mass number of 2, combine to form an isotope of helium with a mass number of 3. The equation for this nuclear reaction is reaction.
2 1H 1
1H :3 2He . Calculate the energy released during this
(Mass of hydrogen-2 nucleus 3.342 1027 kg; mass of hydrogen-1 nucleus 1.673 1027 kg; mass of helium-3 nucleus 5.007 1027 kg.)
