In a certain inorganic substance, the mass fractions of sodium, sulfur, oxygen are, respectively, equal to 32.39%

| September 24, 2021 | education

In a certain inorganic substance, the mass fractions of sodium, sulfur, oxygen are, respectively, equal to 32.39%, 22.53%, 45.07%. Determine the molecular formula of this substance

Let us denote: x is the number of sodium atoms, y is the number of sulfur atoms, z is the number of oxygen atoms, M is the molecular weight of the compound.
The relative atomic mass of sodium is 23, sulfur is 32, oxygen is 16.
Let’s compose the following expressions:
0.3239 = 23 * x / M;

0.2253 = 32 * y / M;

0.4507 = 16 * z / M;

Let us express the molecular weight from three expressions:
M = 23 * x / 0.3239 = 71x;

M = 32 * y / 0.2253 = 142y;

M = 16 * z / 0.4507 = 35.5z;

The values of the unknown numbers: x = 2, y = 1, z = 4. The formula of the substance is Na2SO4.
Answer: the molecular formula of the substance is Na2SO4 (sodium sulfate).



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