\text { 2.57 Calculate } \Delta_{r} H^{\circ} \text { for the dissociation } \mathrm{H}_{2}(\mathrm{~g})=2 \mathrm{H}(\mathrm{g}) at 0, 298, and 3000 K. The value at 0 K is equal to the

spectroscopic dissociation energy D0.