During an experiment, iron powder and sulfur powder were heated together to form a black mass. it was observed that a magnet, when brought near the black mass, did not attract the black mass. which of the following correctly justifies the observation?
a. the black mass is a mixture and no longer retains the properties of iron.
b. the black mass is a mixture and retains the properties of iron.
c. the black mass is a pure substance and no longer retains the properties of iron.
d. the black mass is a pure substance and retains the properties of iron.

The correct answer is option(C).

Explanation:

Compound is a substance made up of two or more elements which are chemically joined together.

When the iron and sulfur heated together in the test tube a chemical reaction reaction took place between the iron and sulfur which lead to the formation of iron sulfur compound (here black mass).And this compound will differ in chemical proprieties with respect to its constituting pure element.

When the magnet was brought near to it , it doesn't attracted the black mass towards itself.This is because the 'The black mass is a compound and no longer retains the properties of iron'.

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.