All practice pages/Interatomic theory
Real compounds that follow the law, worked out step by step. Then practice problems from lab data, and rounds of ten questions.
When two elements form more than one compound, take the same mass of the first element in each compound. The masses of the second element that combine with it are in a ratio of small whole numbers, such as 2 : 1 or 3 : 2.
Multiply by 2, 3 or 4 until the ratio is a whole number. Measured data are never exact, so 1.49 or 2.02 still count as 1.5 and 2.
The law of definite proportions is about one compound: any sample of it has the same composition. The law of multiple proportions compares two different compounds made of the same two elements.