The molar mass of acetone is the summation of the atomic mass of the elements forming it multiplied by its number of atoms.
Atomic mass of C = 12.011 g/mol.
Atomic mass of H = 1.008 g/mol.
Atomic mass of O = 15.999 g/mol.
The molar mass of acetone = [(3 x atomic mass of C) + (6 x atomic mass of H) + (Atomic mass of O)] = [(3 x 12.011 g/mol) + (6x 1.008 g/mol) + (15.999 g/mol)] = 58.08 g/mol.
The mass % of any element = [(no, of the element atoms x atomic mass of the element) / molar mass of the compound] x 100.
∴ The mass % of O = (Atomic mass of O / molar mass of acetone) x 100 = [(15.999 g/mol) / (58.08 g/mol)] = 27.6 %.
Methylcyclopentane consist of 3 types of hydrogen which are 1° (primary), 2° (secondary) and 3° (tertiary) hydrogen atoms. In the chlorination of methylcyclopentane, there are four monochlorinated products possible and two stereoisomers.