During an experiment, solid iodine was placed in a sealed container. The container was gradually heated and purple-colored vapors of iodine formed were observed. Describe this system when it reaches phase equilibrium.

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Explanation:

A system is said to have attained dynamic equilibrium when the rate of forward reaction and the rate of reverse reaction are equal.

Considering the system under consideration;

I2(s)⇄I2(g)

Heating the container converts solid iodine to purple coloured iodine vapour.

At equilibrium, there will be no net change in the amount of solid iodine and iodine vapour present in the system because the two processes (forward and reverse reactions) occur at the same rate at equilibrium.

a corroding iron, if that's one of your choices