21) Atom bomb is based on the principle of
(A) Nuclear fusion
(B) Nuclear fission
(D) Nuclear fission and fusion both
22) Oxidation involves
(A) Gain in electrons
(B) Gain in hydrogen
(C) Loss of electrons
23) The substances are radioactive, which have?
(A) Electrons in their nuclei
(B) Nuclei with less number of neutrons
(C) Unstable nuclei
(D) Electrons removed from the outermost shell
24) When nuclear energy is intended to be harnessed for generation of electricity, potentially destructive neutrons released in a reactor are absorbed by?
(A) Heavy water
(B) Long rods of Cadmium
(C) Cubical blocks of steel
(D) A pile of blocks made of graphite
25) Nuclear power reactors are operated at low temperatures and consequently with lower efficiency because?
(A) Nuclear heat is carried by ordinary steam
(B) Uranium is difficult to heat
(C) The walls of nuclear reactors can not withstand high temperature
(D) High pressure inside the reactor reduces the temperature
26) The energy emitted from the sun supposed to be due to
(A) Nuclear fission
(B) Nuclear fusion
(C) Combustion of hydrogen
(D) Combustion of He
(E) Radioactive disintegration
27) In a hydrogen bomb, hydrogen is converted into?
(C) Uranium — 238
28) When two ice cubes are pressed over each other they unite to form one cube. Which of the following force is responsible for holding them together?
(A) Vander Walls forces
(B) Covalent attraction
(C) Hydrogen bond formation
(D) Dipole dipole attraction
29) The high boiling point of water is due to?
(A) Weak dissociation of water molecule
(B) Hydrogen bonding among water molecules
(C) Its high specific heat
(D) Its high dielectric constant
30) Ice has an open structure compared to water due to which it floats on water and occupies a greater volume of space. The open structure of ice is due to?
(A) Solid state of ice
(B) Its low density
(C) Crystalline nature
(D) Hydrogen bonding