Thorn et al. (J. Phys. Chem. 100, 14178 (1996)) carried out a study of Cl₂O(g) by photoelectron ionization. From their measurements, they report Δ_fH^⦵(Cl₂O)=+77.2 kJmol⁻¹. They combined this measurement with literature data on the reaction Cl₂O (g)+H₂O(g)→2 HOCl(g), for which K=8.2×10⁻² and Δ_rS^⦵ =+16.38 JK⁻¹mol⁻¹, and with readily available thermodynamic data on water vapour to report a value for Δ_fH^⦵(HOCl). Calculate that value. All quantities refer to 298K.