Final answer:
The energy saved by adding the catalyst to the reaction is the difference between the uncatalyzed activation energy (80 kJ) and the catalyzed activation energy (70 kJ), which is 10 kJ.
Step-by-step explanation:
The student asked how much energy is saved by adding a catalyst to a reaction. By using the information provided, we are told that the energy needed to go from the initial state to the transition state is initially 80 kJ for the uncatalyzed reaction (a), and 70 kJ for the catalyzed reaction (b). Since both activation energies for the second steps of the reactions remain the same, at 20 kJ, the difference in energy required for the transition states of the reactions gives us the energy saving afforded by the catalyst.
Thus, the energy saved by adding the catalyst would be the difference between the uncatalyzed and catalyzed activation energies: 80 kJ - 70 kJ = 10 kJ. Therefore, the answer is (a) 10 kJ.