# Calculate the mass fractions of elements in the following compounds: H³PO⁴ Na²SiO³ BaSO⁴ KCIO³.

The mass fraction of an element in a compound is the ratio of the sum of the relative atomic masses (Ar) of all atoms of a given element to the relative molecular mass (Mr). Relative atomic mass is a dimensionless unit. Its numerical value can be found in the periodic system of Mendeleev.

1) Calculate the mass fractions of elements for H3PO4

Ar (H) = 1; Ar (P) = 31; Ar (O) = 16;

Mr (H3PO4) = Ar (H) * 3 + Ar (P) * 1 + Ar (O) * 4 = 1 * 3 + 31 * 1 + 16 * 4 = 3 + 31 + 64 = 98.

ω (H) = (1 * 3) / 98 = 0.03;

ω (P) = (31 * 1) / 98 = 0.32;

ω (O) = (16 * 4) / 98 = 0.65.

2) calculate the mass fractions of elements for Na2SiO3.

Ar (Na) = 23; Ar (Si) = 28; Ar (O) = 16;

Mr (Na2SiO3) = 23 * 2 + 28 * 1 + 16 * 3 = 122.

ω (Na) = (23 * 2) / 122 = 0.38;

ω (Si) = (28 * 1) / 122 = 0.23;

ω (O) = (16 * 3) / 122 = 0.39.

3) calculate the mass fractions of elements for BaSO4.

Ar (Ba) = 137; Ar (S) = 32; Ar (O) = 16;

Mr (BaSO4) = 137 + 32 + 16 * 4 = 233

ω (Ba) = 137/233 = 0.59;

ω (S) = 32/233 = 0.14;

ω (O) = 16 * 4/233 = 0.27.

4) calculate the mass fractions of elements for KClO3.

Ar (K) = 39; Ar (Cl) = 35; Ar (O) = 16;

Mr (KClO3) = 39 + 35 + 16 * 3 = 122.

ω (K) = 39/122 = 0.32;

ω (Cl) = 35/122 = 0.29;

ω (O) = (16 * 3) / 122 = 0.39.