21)Milk is a—
a) mixture
b) element
c) metal
d) none of these
22)Bar is a unit of—
a) pressure
b) force
c) energy
d) frequency
23) Air is –
a)Compound
b) element
c) mixture
d) solution
24) The atoms of the elements having same mass number but different atomic number are called—
a) Isotopes
b) Isobars
c) Isotones
d) Isomers
25)Meson was discovered by—
a) Powell
b) Seaburg
c) Anderson
d) Yukawa
26)Which one of the following element is essential for construction is nuclear reactors?
a) Cobalt
b) Nickel
c) Zirconium
d) Tungsten
27) Group displacement law was given by—
a) Bacquerel
b) Rutherford
c) Mendeleaf
d) Soddy and Fajan
28)The structure of ethylene is—
a) linear
b) tetrahedral
c) octahedral
d) triangular
29)Which one has hydrogen bonding?
a) HCI
b) HBr
c) HF
d) HI
30)Water solution base is called—
a) Acid
b) Salt
c) Alkali
d) None