Q.In the reaction N2 + 3H2 ⇌ 2NH3, the ratio by volume of N2, H2 and NH3 is 1 : 3 : 2 This illustrates the law of a. definite proportion b. reciprocal proportion c. multiple proportion d. gaseous volumes

Step 1. The question gives a simple whole-number VOLUME ratio (1:3:2) between the gases in N2 + 3H2 ⇌ 2NH3.

Step 2. Definite proportion and multiple proportion both concern MASS ratios of combining elements, not gas volumes, so they don't fit here. Reciprocal proportion concerns how two elements that each combine with a third element also relate to each other — also not a volume law. …

Recognise that the question is about a VOLUME ratio between gases, which is the defining feature of Gay-Lussac's …

• Picking 'c. multiple proportion' by pattern-matching on the word 'proportion' in the option text, without notici …