During a hypothetical reaction at constant pressure
CHEMISTRY · Single correct · A Level · Chemistry · Energetics · Energetics
Problem
During a hypothetical reaction at constant pressure, the chemical potential energy of the reactants is 120 kJ, whereas that of the products is 65 kJ. Which statement best describes the enthalpy change and the resulting energy flow?
(a) ΔH is negative because the system’s potential energy decreases, so thermal energy flows to the surroundings and the surroundings warm.
(b) ΔH is positive because the system’s potential energy decreases, so thermal energy flows from the surroundings into the system and the surroundings cool.
(c) ΔH is zero because the decrease in potential energy is exactly balanced by other forms of energy within the system, so no thermal energy is exchanged with the surroundings.
(d) ΔH is negative because the system’s potential energy decreases, so thermal energy flows from the surroundings into the system and the surroundings cool.