Three halogenation reactions of hydrogen at 298 K are shown below
CHEMISTRY · Single correct · A Level · Chemistry · Energetics · Energetics
Problem
Three halogenation reactions of hydrogen at 298 K are shown below.
Reaction X: H₂(g) + F₂(g) → 2 HF(g)
Reaction Y: H₂(g) + Cl₂(g) → 2 HCl(g)
Reaction Z: H₂(g) + Br₂(g) → 2 HBr(g)
Average bond energies (kJ mol⁻¹): H–H 436, F–F 159, Cl–Cl 242, Br–Br 193, H–F 567, H–Cl 431, H–Br 368
Which of the following correctly lists the reactions in order from most exothermic to least exothermic?
(a) Z>Y>X
(b) Y>X>Z
(c) X>Y>Z
(d) X>Z>Y