Calculate the mass fractions in oxygen H2SO4, Al2 (SO4) 3.

The mass fraction of oxygen in these compounds is equal to the ratio of the molar masses of oxygen atoms to the molar mass of these substances.

Sulfuric acid.

Let’s find the molar mass of the substance and the oxygen atoms that make up the sulfuric acid.

M H2SO4 = 2 + 32 +16 x 4 = 98 grams / mol;

M O4 = 16 x 4 = 64 grams / mol;

K1 = M O4 / M H2SO4 = 64/98 = 0.653 = 65.3%;

Aluminum sulfate.

Let’s find the molar mass of the substance and oxygen atoms included in the aluminum sulfate.

M Al2 (SO4) 3 = 27 x 2 + (32 + 16 x 4) x 3 = 342 grams / mol;

M O12 = 16 x 12 = 192 grams / mol;

K2 = M O12 / M Al2 (SO4) 3 = 192/342 = 0.5614 = 56.14%;