Derive the chemical formula of a substance if it is known that it contains 37.7% sodium, 23%

| September 19, 2021 | education

Derive the chemical formula of a substance if it is known that it contains 37.7% sodium, 23% silicon and 39.3% oxygen. The relative molecular weight of the substance is 122 g.

Let the numbers of sodium, silicon and oxygen atoms in the empirical formula be x, y, z – NaxSiyOz.
The atomic masses of potassium, chlorine and oxygen are 22.99; 28.08; 16 – respectively.
22.99x: 28.08y: 16Z = 37.7: 23: 39.3.
Let’s divide by the corresponding coefficients:
x: y: z = 37.7 / 22.99: 23 / 28.08: 39.3 / 16.
x: y: z = 1.639: 0.819: 2.456.
Let’s divide by a smaller coefficient:
x: y: z = 1.639 / 0.819: 0.819 / 0.819: 2.456 / 0.819.
x: y: z = 2: 1: 3.
The formula of the substance is Na2SiO3.
Let’s define its molar mass:
M (Na2SiO3) = 22.99 * 2 + 28.08 + 16 * 3 = 122 g.
The empirical formula fits in terms of molar mass.
Answer: the formula of the substance is Na2SiO3.



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