The correct option is (c).
Explanation
The properties of a mixture of elements and a chemical compound formed from those elements. When Iron (Fe) and Sulphur (S) are heated together, they undergo a chemical reaction to form a new compound called Iron(II) sulphide (FeS), which possesses properties distinct from its constituent elements.- Statement 1 is Correct: The compound formed, Iron(II) sulphide (FeS), is a hard, black solid. This visual change indicates that a chemical reaction has occurred, distinguishing it from the yellow powder of sulphur and the grey colour of iron.
- Statement 2 is Incorrect: While elemental Iron is ferromagnetic and strongly attracted to a magnet, the compound Iron sulphide is not magnetic. In a chemical compound, the individual properties of the constituent elements are lost. If this were a physical mixture of iron filings and sulphur powder, the iron would still be attracted to a magnet.
- Statement 3 is Correct: A fundamental characteristic of a chemical compound is that it follows the Law of Definite Proportions (or Constant Composition). The elements Iron and Sulphur combine in a fixed ratio by mass (approximately 7:4) to form Iron sulphide. Unlike a mixture, the composition of a pure compound does not vary.
Key Takeaway: A chemical compound exhibits properties entirely different from its constituent elements and always maintains a fixed chemical composition, whereas a mixture retains the properties of its components and has a variable composition.