For the gas-phase reaction pattern X₂(g) + 2 HBr(g) → 2 HX(g) + Br₂(g) (X is a…
CHEMISTRY · Single correct · A Level · Chemistry · Energetics · Energetics
Problem
For the gas-phase reaction pattern
X₂(g) + 2 HBr(g) → 2 HX(g) + Br₂(g)
(X is a halogen other than Br), a chemist must choose the halogen X that makes the reaction enthalpy as close to zero as possible at 298 K. Use the following average bond energies (kJ·mol⁻¹):
H–F 565 H–Cl 431 H–I 299
F–F 159 Cl–Cl 242 I–I 151 Br–Br 193
Which halogen should be selected?
(a) I₂
(b) Cl₂
(c) F₂
(d) At₂