See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the thermodynamic outcome (exergonic vs endergonic): In both Reaction A and Reaction B, the products are at a lower energy level than the reactants. This means both reactions are exergonic (energy-releasing), not endergonic. This immediately eliminates options (c) and (d), which describe the reactions as endergonic. Step 2 - Compare the degree of exergonicity: The difference in energy between reactants and products represents the overall free energy change (ΔG). In Reaction B, the products are at a much lower energy level relative to the reactants compared to Reaction A. Therefore, Reaction B is MORE exergonic than Reaction A, meaning Reaction A is LESS exergonic than Reaction B. Step 3 - Compare the reaction rates (activation energy): The rate of a reaction is determined by the height of the activation energy barrier (the energy difference between the reactants and the highest transition state peak). In Reaction A, there is one transition state peak, and its height above the reactants appears relatively modest. In Reaction B, there are two transition state peaks, and the highest peak (first peak) is significantly higher than the single peak in Reaction A. A higher activation energy means a slower reaction. Therefore, Reaction A has a lower activation energy and is FASTER than Reaction B. Step 4 - Match to the options: Reaction A is faster (lower activation energy) and less exergonic (smaller drop in energy from reactants to products) than Reaction B. This matches option (a). Why other options fail: - (b) says Reaction B is faster: incorrect, Reaction B has a higher activation energy barrier. - (c) says reactions are endergonic: incorrect, both are exergonic. - (d) says reactions are endergonic: incorrect, both are exergonic. Therefore, the correct answer is A.