What is the percent mass oxygen in acetone

27.6 %.

Explanation:

Acetone has the molecular formula (C₃H₆O). 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 %.