Chemistry - Mole Concept Question with Solution | TestHub

The law of reciprocal proportions (also known as Richter's law) states that if two elements (A and B) combine separately with a fixed mass of a third element (C), then the ratio of the masses in which A and B combine with each other is either the same as or a simple multiple of the ratio of the masses in which they combine separately with the third element.

Let's analyze option C: MgO, Mg₃N₂, N₂O₃.

Here, the three elements are Magnesium (Mg), Nitrogen (N), and Oxygen (O).

1. Mg and O combine to form MgO.

2. Mg and N combine to form Mg₃N₂.

3. N and O combine to form N₂O₃.

This set of compounds illustrates the law of reciprocal proportions because it involves three different elements combining with each other in pairs.

The other options (A, B, D) primarily show different compounds formed between only two elements (Law of Multiple Proportions) or do not involve three distinct elements combining in pairs as required by the Law of Reciprocal Proportions.

The final answer is C.