Question

which chemical changes are reversible?

Answer 1

Because chemical changes produce new substances, they often cannot be undone. For example, you can't change ashes from burning logs back into wood. Some chemical changes can be reversed, but only by other chemical changes. For example, to undo tarnish on copper pennies, you can place them in vinegar.

Answer 2

N2+ 3 H2 ⇋ 2 NH3(This reaction is involved in Haber's Process)

Is an Example of Reversible chemical change.