The observations are as follows:
When a mixture of iron fillings and sulfur are heated, black iron (ii) sulfide is formed.
Unlike iron fillings, black iron (ii) sulfide is not attracted to a magnet.
When carbon sulfide is added to it, no visible reaction is observed.
When dilute hydrochloric acid is added to it, a gas with a rotten-egg smell is evolved.
The gas is hydrogen sulfide which is a reducing agents and acidic in nature.
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