Establish the formula of the compound if it is known that the mass ratios of sodium, nitrogen and oxygen in it are 11.5: 7: 24

Decision:
1. Let’s designate: x – molecular weight of a compound, a – number of sodium atoms, b – number of nitrogen atoms, c – number of oxygen atoms.
2. The relative atomic mass of sodium is 23, nitrogen is 14, oxygen is 16.
3. The total compound contains 42.5 parts. Sodium is 11.5 / 42.5 = 0.2706. Nitrogen is 7 / 42.5 = 0.1647. Oxygen is 24 / 42.5 = 0.5647.
4. Let’s compose the following expressions:
0.2706 = (23 * a) / x;
0.1647 = (14 * b) / x;
0.5647 = (16 * s) / x;
1. Let’s express the molecular weight:
x = (23 * a) / 0.2706 = 85a;
x = (14 * b) / 0.1647 = 85b;
x = (16 * s) / 0.5647 = 28.33c;
Equating expressions: 85a = 85b = 28.33c. Therefore: a = 1, b = 1, c = 3. The starting compound is sodium nitrate, its formula is NaNO3.
Answer: the formula of the compound is NaNO3.