The correct option for the question is **A. law of multiple proportions**. ### Explanation of the Correct Answer The law of multiple proportions states that when two elements combine to form more than one compound, the ratios of the masses of one element that combine with a fixed mass of the other element can be expressed as ratios of small whole numbers. In this case, element X forms three different compounds with chlorine: XCl4, XCl3, and XCl2. Here’s how we can analyze this: 1. **Identifying the Compounds**: - XCl4 contains 4 chlorine atoms. - XCl3 contains 3 chlorine atoms. - XCl2 contains 2 chlorine atoms. 2. **Understanding the Ratios**: - If we take a fixed amount of element X (let's say 1 mole of X), we can look at how much chlorine is combined with it in each compound: - For XCl4: 1 mole of X combines with 4 moles of Cl. - For XCl3: 1 mole of X combines with 3 moles of Cl. - For XCl2: 1 mole of X combines with 2 moles of Cl. 3. **Calculating the Ratios**: - The ratios of chlorine in these compounds can be expressed as: - XCl4 to XCl3: 4:3 - XCl4 to XCl2: 4:2 (which simplifies to 2:1) - XCl3 to XCl2: 3:2 These ratios (4:3, 4:2, and 3:2) are all whole numbers, which is a key aspect of the law of multiple proportions. ### Why the Other Options are Incorrect **B. Law of chemical proportions**: - This law, also known as the law of definite proportions, states that a chemical compound always contains its component elements in fixed ratio by mass. This law does not apply here because we are discussing multiple compounds formed by the same elements, not a single compound with a fixed ratio. **C. Law of simple proportions**: - This term is not commonly used in chemistry. It may refer to the idea of ratios in simple compounds, but it does not specifically address the situation where multiple compounds are formed from the same elements. Therefore, it is not applicable in this context. **D. Law of conservation of mass**: - This law states that mass is neither created nor destroyed in a chemical reaction. While this is a fundamental principle of chemistry, it does not relate to the formation of multiple compounds from the same elements. It does not explain the ratios of elements in different compounds. ### Summary of Key Points - The law of multiple proportions applies when two elements form more than one compound, and the ratios of the masses of one element that combine with a fixed mass of the other can be expressed as small whole numbers. - In the case of XCl4, XCl3, and XCl2, the ratios of chlorine atoms are whole numbers, illustrating this law. - The other options do not accurately describe the situation presented in the question. ### Revision Summary - **Law of Multiple Proportions**: When two elements form multiple compounds, the mass ratios of one element with a fixed mass of the other are whole numbers. - **Example**: XCl4, XCl3, and XCl2 show different ratios of chlorine with the same element X. - **Incorrect Options**: - Law of chemical proportions refers to fixed ratios in a single compound. - Law of simple proportions is not a standard term in chemistry. - Law of conservation of mass pertains to mass in reactions, not compound formation.