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. **Identify the Compounds**: - XCl4: This compound contains 4 chlorine atoms for every 1 atom of element X. - XCl3: This compound contains 3 chlorine atoms for every 1 atom of element X. - XCl2: This compound contains 2 chlorine atoms for every 1 atom of element X. 2. **Mass Ratios**: - If we consider a fixed mass of X (let's say 1 mole of X), we can calculate the mass of chlorine in each compound: - For XCl4: Mass of Cl = 4 × (mass of Cl atom) - For XCl3: Mass of Cl = 3 × (mass of Cl atom) - For XCl2: Mass of Cl = 2 × (mass of Cl atom) 3. **Comparing Ratios**: - The ratios of the masses of chlorine in these compounds can be expressed as: - Cl in XCl4 : Cl in XCl3 = 4 : 3 - Cl in XCl3 : Cl in XCl2 = 3 : 2 - These ratios (4:3 and 3:2) are 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 dealing with multiple compounds of 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 of multiple compounds formed by the same elements. Therefore, it is not a recognized law in the context of chemical compounds. **D. Law of conservation of mass**: - This law states that mass is neither created nor destroyed in a chemical reaction. While it 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, showing that the ratios of the masses of one element can be expressed as small whole numbers. - In this case, XCl4, XCl3, and XCl2 illustrate this law through the different ratios of chlorine atoms combined with the same element X. - The other options do not accurately describe the relationship between the compounds formed by element X and chlorine. ### Revision Summary - **Law of Multiple Proportions**: Ratios of masses of elements in different compounds can be expressed as small whole numbers. - **Example Compounds**: XCl4, XCl3, XCl2 demonstrate this law with varying amounts of chlorine. - **Incorrect Options**: Law of chemical proportions, law of simple proportions, and law of conservation of mass do not apply to this scenario.