An element X forms the following compounds with chlorine; XCl$_4$, XCl$_3$, XCl$_2$. This illustrates the

Analysis of the Question

The question asks us to identify the chemical law demonstrated when a single element (X) combines with another element (chlorine) to form more than one compound with different ratios of the elements.

Concept Explanation

The Law of Multiple Proportions states that when two elements combine to form more than one compound, the masses of one element that combine with a fixed mass of the other are in a ratio of small whole numbers.

In this scenario:

• We have element X and element Cl.
• They form three distinct compounds: XCl$_2$, XCl$_3$, and XCl$_4$.
• If we fix the mass of X at 1 mole, the ratios of the mass of chlorine in these compounds are 2:3:4.
• Because these are small whole numbers, this is a classic illustration of the Law of Multiple Proportions.

Step-by-Step Solution

1. Identify the components: We have one element (X) reacting with another (Cl).
2. Observe the pattern: The element X is forming multiple compounds with the same second element (Cl).
3. Apply the definition: Whenever you see an element forming different compounds with another element (like CO and CO$_2$, or in this case, XCl$_2$, XCl$_3$, and XCl$_4$), it is the definition of the Law of Multiple Proportions.
4. Evaluate the options: • Law of Multiple Proportions: Fits perfectly as it deals with multiple compounds formed by the same two elements. • Law of Chemical Proportions: This is a general term, not a specific scientific law. • Law of Simple Proportions: This is often confused with the Law of Definite Proportions, but it is not the standard name for this phenomenon. • Law of Conservation of Mass: This states that matter is neither created nor destroyed in a chemical reaction; it does not describe the formation of multiple compounds.

Conclusion

The correct option is A.

Exam Tip

Whenever you see a question involving two elements forming different compounds (e.g., $XY$, $XY_2$, $XY_3$), immediately look for "Multiple Proportions" in the options. It is a favorite topic for JAMB examiners!