The average $\mathrm{O}-\mathrm{H}$ bond energy in  ${\mathrm{H}}_2\mathrm{O}$ with the help of following data:

(P) ${\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)⟶{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right); \mathrm{\Delta H}=+40.6\mathrm{kJ}{\mathrm{mol}}^{-1}$

(Q) $2\mathrm{H}\left(\mathrm{g}\right)⟶{\mathrm{H}}_2\left(\mathrm{g}\right);\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\mathrm{\Delta H}=-435.0{\mathrm{kJmol}}^{-1}$

(R) ${\mathrm{O}}_2\left(\mathrm{g}\right)⟶2\mathrm{O}\left(\mathrm{g}\right);\mathrm{\Delta H}=+489.6\mathrm{kJ}{\mathrm{mol}}^{-1}$

(S) $2{\mathrm{H}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)⟶2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) ; \mathrm{\Delta H}=-571.6\mathrm{kJ}{\mathrm{mol}}^{-1}$