Nuclei

Fission of nuclei is possible because the binding energy per nucleon in them

1. increases with mass number at low mass numbers
2. decreases with mass number at low mass numbers
3. increases with mass number at high mass numbers
4. decreases with mass number at high mass numbers.

Which one of the following pairs of nuclei are isotones ?

1. 34Se74, 31Ga71
2. 38Sr84, 38Sr86
3. 42Mo92, 40Zr92
4. 20Ca40, 16S32

If M(A, Z), Mp and Mn denote the masses of the nucleus AZX, proton and neutron respectively in units of u (1 u = 931.5 MeV/c2) and BE represents its binding energy in MeV, then

1. M(A, Z) = ZMp + (A - Z)Mn - BE
2. M(A, Z) = ZMp + (A - Z)Mn + BE/c2
3. M(A, Z) = ZMp + (A - Z)Mn - BE/c2
4. M(A, Z) = ZMp + (A - Z)Mn + BE

If in a nuclear fusion process the masses of the fusing nuclei be m1 and m2 and the mass of the resultant nucleus be m3, then

1. m3 = m1 + m2
2. m3 = |m1 - m2|
3. m3 < (m1 + m2)
4. m3 > (m1 + m2)

A nucleus represented by the symbol AZX has

1. Z neutrons and A - Z protons
2. Z protons and A - Z neutrons
3. Z protons and A neutrons
4. A protons and Z - A neutrons

The half life of radium is about 1600 years. Of 100 g of radium existing now, 25 g will remain unchanged after

1. 4800 years
2. 6400 years
3. 2400 years
4. 3200 years

Solar energy is mainly caused due to

1. burning of hydrogen in the oxygen
2. fission of uranium present in the Sun
3. fusion of protons during synthesis of heavier elements
4. gravitational contraction

The volume occupied by an atom is greater than the volume of the nucleus by a factor of about

1. 101
2. 105
3. 1010
4. 1015

The mass of proton is 1.0073 u and that of neutron is 1.0087 u (u = atomic mass unit). The binding energy of 42He is (Given helium nucleus mass ≈ 4.0015 u.)

1. 0.0305 J
2. 0.0305 erg
3. 28.4 MeV
4. 0.061 u

A sample of radioactive element has a mass of 10 g at an instant t = 0. The approximate mass of this element in the sample after two mean lives is

1. 1.35 g
2. 2.50 g
3. 3.70 g
4. 6.30 g