The mass fractions of potassium, phosphorus and oxygen in a certain compound

| September 25, 2021 | education

The mass fractions of potassium, phosphorus and oxygen in a certain compound are 55.19: 14.62 and 30.19%, respectively. Determine its simplest formula.

Let us denote: x is the number of potassium atoms, y is the number of phosphorus atoms, z is the number of oxygen atoms, M is the molecular weight of the compound. The relative atomic mass of potassium is 39, phosphorus is 31, and oxygen is 16.
Let’s compose the following expressions:
0.5519 = 39 * x / M;

0.1462 = 31 * y / M;

0.3019 = 16 * z / M;

Let us express the molecular weight from three expressions:
M = 39 * x / 0.5519 = 70.666x;

M = 31 * y / 0.1462 = 212y;

M = 16 * z / 0.3019 = 53z;

Equating the obtained expressions, we get: x = 3, y = 1, z = 4. The formula of the salt is K3PO4.
Answer: The salt formula is K3PO4.



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