a) In a typical nuclear reaction, e.g. , 
Although number of nucleons is conserved, yet energy is released. How? Explain.
b) Show that nuclear density in a given nucleus is independent of mass number A.a)
In a nuclear reaction,
In a nuclear reaction, the sum of the masses of the of the target nucleus and the bombarding particle may be greater or less than the sum of masses of the product nucleus and the outgoing particle. Therefore, from the law of conservation of mass-energy around 3.27 MeV is evolved or involved in a nuclear reaction. This energy is called the Q-value of the nuclear reaction.
Cause of the energy released:
i) Binding energy per nucleon of becomes more than the BE/A of 
ii) Mass defect between the reactant and the product nuclei.
b) The radius of nucleus of mass number A is given by R = 
Volume of the nucleus, 
Density of the matter in the nucleus is given by,
Hence, density is independent of mass number A.
