What new substance is formed when a mixture of iron filings and sulfur powder is heated, and how is it different from the original mixture? Also, write the word equation for the reaction.
When a mixture of iron filings and sulfur powder is heated, a new substance called iron sulfide is formed.
Iron sulfide is different from the original mixture in the following ways:
(1) It has a uniform black colour throughout, unlike the mixture where yellow sulfur and black iron particles were visible separately.
(2) Iron sulfide is not attracted by a magnet, whereas iron filings in the mixture were magnetic.
(3) When treated with dilute hydrochloric acid, iron sulfide produces hydrogen sulfide gas with a rotten egg smell, while the mixture produces hydrogen gas with a pop sound.
Word equation: Iron + Sulfur → Iron sulfide (on heating)
Explanation
Activity 8.5 in the chapter demonstrates this reaction. Sample A (mixture of iron and sulfur) retains individual properties - iron is attracted to magnet and produces hydrogen gas with acid. Sample B (iron sulfide) is a compound with completely different properties - not magnetic and produces hydrogen sulfide gas with acid. The chapter states that 'a compound has been formed' with 'completely different properties.'
Solution Steps
Iron sulfide forms when a mixture of iron filings and sulfur powder is heated
Iron sulfide has a uniform black colour, unlike the mixture where yellow sulfur and black iron particles were visible separately
Iron sulfide is not attracted by a magnet, unlike iron filings in the mixture which were magnetic
Iron sulfide produces hydrogen sulfide gas (rotten egg smell) with dilute hydrochloric acid, while the mixture produces hydrogen gas (pop sound)
Word equation: Iron + Sulfur → Iron sulfide (on heating)