Two nuclei of mass number 3 combine with another nucleus of mass number 4 to yield a nucleus of mass number 10. If the binding energy per nucleon for the mass numbers 3, 4 and 10 are 5.6 MeV, 7.4 MeV and 6.1 MeV, respectively, then in the process, Mc2= MeV.
- 6.9
- 7.9
- 2.2
- 4.3
Answer
(3) 2.2
Solution
Binding energy (BE) = (BE per nucleon) × (mass number)
Reactants (two nuclei with A = 3 and one with A = 4):
BEi=2 (3 5.6)+4 7.4=33.6+29.6=63.2 MeV
Product (A = 10): BEf=10 6.1=61.0 MeV
∵ BEf<BEi, the product is less tightly bound; the mass of the system increases and energy must be supplied:
Mc2=BEi-BEf
⇒ Mc2=63.2-61.0=2.2 MeV
Answer: (3)