CHEMISTRY · Single correct · A Level · Chemistry · Energetics · Energetics
Problem
In the one-step reaction X–Y+Z→X+Y–Z, the largest energy input on the reaction’s potential-energy profile occurs early along the reaction pathway. Which bond change is primarily responsible for that energy input?
(a) Breaking the Y–Z bond, because the strongest bonds are broken in the products.
(b) Reorienting the reactant molecules to overcome initial electron–electron repulsion during the collision.
(c) Breaking the X–Y bond, because bond breaking requires energy absorption.
(d) Forming the Y–Z bond, because bond formation requires a large energy input before energy is released.