Law of Multiple Proportions — Prelims Strategy

Prelims Strategy

For NEET prelims questions on the Law of Multiple Proportions, a clear conceptual understanding is paramount. First, ensure you can accurately state the law and its conditions: two elements, forming more than one compound, with variable masses of one element combining with a fixed mass of the other in a simple whole-number ratio.

For numerical problems, the strategy involves three key steps: 1) Identify the two elements and the compounds they form. 2) Fix the mass of one element (usually the one whose mass is given as constant, or calculate it for 1 gram/unit if percentages are given).

This often involves scaling the given masses. 3) **Calculate the ratio of the masses of the *other* element** that combine with the fixed mass. This ratio *must* be simplified to its lowest whole numbers.

If it's a simple whole-number ratio (e.g., 1:2, 2:3), the law is obeyed. Be careful with decimal calculations and ensure the final ratio is indeed simple and whole-numbered. For conceptual questions, focus on distinguishing this law from the Law of Definite Proportions (multiple compounds vs.

single compound) and its direct link to Dalton's Atomic Theory. Practice identifying correct and incorrect examples of the law's application.