Two chemical substances X and Y combine together to form a product P which contains both X and Y :
X + Y → P
X and Y cannot be broken down into simpler substances by simple chemical reactions. Which of the following statements concerning X, Y and P are correct?
(i) P is a compound
(ii) X and Y are compounds
(iii) X and Y are elements
(iv) P has a fixed composition

Question

Accepted Answer

Option 4 is the correct answer, which includes statements (i), (iii), and (iv). Let's break down why this option is correct and why the others are not.

1. **Explanation for Option 4:**

- **(i) P is a compound:** This statement is correct because a compound is a substance formed when two or more elements are chemically bonded together. In the given reaction, X and Y combine to form P, which means P is a compound containing both X and Y.

- **(iii) X and Y are elements:** This statement is correct because elements are substances that cannot be broken down into simpler substances by simple chemical reactions. The problem states that X and Y cannot be broken down further, indicating that they are elements.

- **(iv) P has a fixed composition:** This statement is correct because compounds have a fixed composition. This means that the ratio of elements in a compound is always the same. Since P is a compound formed from X and Y, it will have a fixed composition.

2. **Why the other options are incorrect:**

- **Option 1 (i), (ii), and (iii):** This option is incorrect because it includes statement (ii), which claims that X and Y are compounds. This contradicts the information given in the question that X and Y cannot be broken down into simpler substances, which is a characteristic of elements, not compounds.

- **Option 2 (i), (ii), and (iv):** This option is incorrect for the same reason as Option 1. It includes statement (ii), which incorrectly identifies X and Y as compounds.

- **Option 3 (ii), (iii), and (iv):** This option is incorrect because it includes statement (ii), which is incorrect for the reasons mentioned above. Additionally, it excludes statement (i), which is correct as P is indeed a compound.

In summary, Option 4 is the only option that correctly identifies P as a compound, X and Y as elements, and acknowledges that P has a fixed composition. This aligns with the fundamental definitions of elements and compounds in chemistry.