The standard heats of formation of $\mathrm{H}_{2} \mathrm{O}(g), \mathrm{H}_{2} \mathrm{S}(g), \mathrm{H}_{2} \mathrm{Se}(g)$ and $\mathrm{H}_{2} \mathrm{Te}(g)$ are $-241.8,-20.17,+29.7,$ and $+99.6 \mathrm{kJ} /$ mol, respectively. The enthalpies necessary to convert the elements in their standard states to one mole of gaseous atoms are $248,277,227,$ and 197 $\mathrm{kJ} / \mathrm{mol}$ atoms for $\mathrm{O}, \mathrm{S},$ Se, and Te, respectively. The enthalpy for dissociation of $\mathrm{H}_{2}$ is 436 $\mathrm{kJ} / \mathrm{mol} .$ Calculate the average $\mathrm{H}-\mathrm{O}, \mathrm{H} \mathrm{S}, \mathrm{H}-\mathrm{Se}$ and $\mathrm{H}-$ Te bond enthalpies, and comment on their trend.