Question

What substance would need to be added in order to reverse the reaction?

Answer 1

The substance that would be added in order to reverse the reaction would be any substance that is found in the product side. Adding a substance that tends to be a product will shift the equilibrium of the system and will allow the reaction to produce the substances that is found in the reactant side.

Answer 2

The right answer is water.

A condensation reaction can sometimes release as a product a molecule of water. We sometimes speak of synthesis by dehydration. This is, for example, the case for two monosaccharides, such as glucose or fructose, which can condense into a disaccharide (sucrose) via dehydration synthesis. The reverse reaction is then hydrolysis, the water recombining with the two hydroxyl groups, the disaccharide being converted back into two monosaccharides.