The masses of neutron and proton are 1.0087 amu and 1.0073 amu respectively. If two neutrons and two protons combine to form a helium nucleus of mass 4.0015 amu, the B.E. of the helium nucleus will be

Q: The masses of neutron and proton are 1.0087 amu and 1.0073 amu respectively. If two neutrons and two protons combine to form a helium nucleus of mass 4.0015 amu, the B.E. of the helium nucleus will be

(a) 28.4 MeV

(b) 20.8 MeV

(c) 27.1 MeV

(d) 14.2 MeV

Sol: (a) 2 ₀ n¹ + 2 ₁ p¹ → ₂ He⁴

Mass defect : Δm = (2 × 1.0087 + 2 × 1.0073 – 4.0015)

= 0.0305 amu

B. E. = 0.0305 × 931 = 28.4 Me V