What are the typical signs a reaction has gone to completion?

The signs that a reaction has gone to completion can often be observed through several distinct changes in the reaction mixture. The disappearance of starting materials indicates that reactants have been converted into products; this can be visually confirmed by comparing the initial state of the reactants with the final state of the mixture.

Additionally, the formation of a precipitate is a physical indication that a new product has formed, which can happen when two soluble reactants combine to yield an insoluble product. A change in color can also signal that a reaction has occurred, particularly in cases where reactants or products possess different colors or where a transformation alters the electronic structure of the molecules involved.

These observable factors collectively confirm that the reaction is complete, as they clearly indicate that a transformation has taken place and that the reactants are no longer present in their original form. This makes option B the most comprehensive choice for indicating completion of a chemical reaction.