Chemistry / Unit 2 Chem 0187 short lesson, about 20 seconds
The Law of Multiple Proportions
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The idea
When two elements form more than one compound, the second element's combining masses per fixed mass of the first form a small whole-number ratio.
In practice
Chlorine combines with copper in a 0.558-to-1 ratio in one compound, 1.116-to-1 in another — a 2-to-1 ratio of ratios.
Where people slip
The ratio compares masses across two compounds, not atoms within one — confusing the two misreads the law.
Your place on the trail
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