You are working in your laboratory and decide to do some cleaning. you find a test tube with some brown substance congealed at the bottom. you take a piece of iron wool to scrub it out, but cannot remove it. you leave the iron wool in the test tube and set it aside to clean your beakers instead. you do not realize the test tube is next to the heater and after a few minutes, a brown gas starts smoking out of the test tube, followed by a reddish-brown gas. upon observation, the iron wool is coated in a yellow-brown substance. you realize that the mystery substance was
a. bromine (br) b. iodide (i) c. argon (ar) d. scandium (sc)

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explanation:

answer:

the reaction is type of combination reaction.

explanation:

on the product side, there are 2 molecules of bonded to fe   which means one atom of fe are combined two molecules of . so, balanced chemical equation becomes :

this reaction follows the reaction type of combination reaction. a combination reaction is defined as chemical reaction in which reactants combines together to form a single product.

the formula mass of a molecule or a compound is the sum of the atomic weights of the atoms in its empirical formula

(that's what i know about formula mass)