Final answer:
The change in Gibb's free energy (ΔG) is additive in sequential reactions, meaning the total free energy change for a process that occurs in steps is the sum of ΔG values for each step.
Step-by-step explanation:
The change in Gibb's free energy (ΔG) is additive in sequential reactions. This property allows us to calculate the total free energy change for a process that occurs in multiple steps by summing the ΔG values for each individual step. For example, let's consider a three-step reaction sequence where:
Step 1: A → B, ΔG1
Step 2: B → C, ΔG2
Step 3: C → D, ΔG3
The total ΔG for the overall reaction A → D would be the sum of ΔG1, ΔG2, and ΔG3. This is because thermodynamic state functions, like Gibb's free energy, are path-independent. The overall free energy change only depends on the initial and final states, not on the specific pathway or the number of steps.
As an example, we can look at the coupling of two reactions: the decomposition of ZnS and the formation of H2S. If we know the ΔG for each reaction, we can add them to determine if the coupled reaction is spontaneous under standard conditions.