a) Ethyne
Molar mass of C2H2 = 2 x atomic mass of C + 2 x atomic mass of H
= 2 x 12 + 2 x 1
= 26u
b) Sulphur molecule
Molar mass of S8 = 8 x atomic mass of S
= 8 x 32
= 256u
c) Phophorous molecule
Molar mass of P4 = 4 x atomic mass of P
= 4 x 31
= 124u
d) Nitric acid
Molar mass of HCl = atomic mass of Cl + atomic mass of H
= 35.5 + 1
= 36.5u