Question

In order to be coupled and run spontaneously, two reactions __________.

1) must have an overall positive ΔG
2) must have an overall negative ΔG
3) a product in the first reaction must be a reactant in the second
4) must have a common reactant

Answer 1

In order for two reactions to be coupled and run spontaneously, the product of one reaction must be a reactant in the other.

Step-by-step explanation:

A spontaneous reaction is one that releases free energy, and so the sign of ΔG must be negative. There are four different possibilities for ΔG:

1. ΔG > 0: The reaction is non-spontaneous.
2. ΔG = 0: The reaction is at equilibrium.
3. ΔG < 0: The reaction is spontaneous.
4. (3) The product of one reaction must be a reactant in the other: This is known as coupling reactions. By coupling an exergonic reaction (ΔG < 0) with an endergonic reaction (ΔG > 0), both reactions can occur spontaneously.