Calculate the mass fraction of silicon and oxygen in silicon oxide (IV).

Formula for calculating the mass fraction of an element in a substance:

w = n * Ar (chemical element) / Mr (substance), where n is the number of atoms of a given chemical element.

1) Find the relative molecular weight of the substance (silicon oxide (IV)):

Mr (PO2) = Ar (P) + 2 * Ar (O) = 31 + 32 = 64

2) Find the mass fraction of this element in the substance:

a) silicon

w (P) = 31/64 = 0.48 or 48%

b) oxygen

1st way: w (O) = 2 * 16/64 = 0, 52 or 52%

2nd method: 100% – 48% = 52%

Answer: mass fraction of silicon = 48%, mass fraction of oxygen = 52%.