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Difficulty: EasyDistinction Between Elements, Compounds, and Mixtures

A student heats a mixture of iron filings and sulfur powder in a test tube until a black solid, iron(II) sulfide, is formed. What property of the resulting black solid confirms that a compound, rather than a mixture, has been produced?

  1. A
    It retains the magnetic attraction of iron and the yellow color of sulfur.
  2. It possesses chemical properties entirely different from its constituents and cannot be separated by physical methods.Answer
  3. C
    It contains iron and sulfur combined in variable proportions depending on how long it was heated.
  4. D
    It is formed without any release or absorption of heat energy during the process.

Answer

The black solid (iron(II) sulfide) is a compound because it possesses distinct chemical properties from iron and sulfur and cannot be separated into its constituent elements by physical methods.
When iron and sulfur chemically react upon heating, iron(II) sulfide (FeSFeS) is formed. Compounds have entirely different properties from their constituent elements and cannot be separated into those elements by physical methods such as using a magnet.

Step-by-Step Solution

1
Analyze the difference between physical mixing and chemical combination of iron and sulfur.
Before heating, iron filings and sulfur form a mixture where iron remains magnetic and sulfur remains soluble in carbon disulfide.
Components in a mixture retain their individual identity and physical properties.
2
Evaluate the effect of heating the mixture to form iron(II) sulfide (FeSFeS).
Heating causes a chemical reaction forming FeSFeS, a compound with a fixed ratio of elements, new properties, and no magnetic attraction for iron.
Chemical bonds are formed in compounds, altering constituent properties completely and preventing physical separation.

Key Concept

Distinction between compounds and mixtures based on physical separation and retention of properties
Estimated Time:50s
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Topics

Distinction Between Elements, Compounds, and Mixtures