$\therefore \,\,\,\Delta {H_f} = \,\,[\frac{1}{2}\,\,{\Delta _{H - H}} + \,\,\frac{1}{2}\,\,\Delta {H_{Cl - Cl}}]\,\, - \,\,[\Delta {H_{Cl - Cl}}]$
$\,\,\,\therefore \,\, - 90\,\, = \,\,[\,\frac{1}{2}\, \times \,\,430\,\, + \,\,\frac{1}{2}\, \times \,\,240]\,\, - \,\,\Delta {H_{Cl - Cl}}$
$- 90 = 215 + 120 -$ $\Delta$$H_{Cl - Cl}$
$- \Delta$ $H_{Cl - Cl}$
$ = 335 + 90 = 425\, KJ/$મોલ
$2Fe + 1/2{O_2} \to F{e_2}{O_3} + y\,kcal$ હોય, તો $Fe$ અને ઓક્સિજન માંથી$F{e_2}{O_3}$ ના સર્જનની ઉષ્મા ... થશે.
$\frac{1}{2}C{l_2}_{(g)}\,\xrightarrow{{\frac{1}{2}{\Delta _{diss}}{H^\Theta }}}\,Cl_{(g)}\,\,\xrightarrow{{{\Delta _{eg}}{H^\Theta }}}\,\,C{l^ - }_{(g)}\,\xrightarrow{{{\Delta _{hyd}}{H^\Theta }}}\,C{l^ - }_{(aq)}$
$({\mkern 1mu} {\Delta _{diss}}{\mkern 1mu} H_{C{l_2}}^\Theta {\mkern 1mu} = {\mkern 1mu} {\mkern 1mu} 240{\mkern 1mu} {\mkern 1mu} kJ{\mkern 1mu} {\mkern 1mu} mo{l^{ - 1}},{\mkern 1mu} {\mkern 1mu} {\Delta _{eg}}{\mkern 1mu} H_{Cl}^\Theta {\mkern 1mu} = {\mkern 1mu} {\mkern 1mu} - 349{\mkern 1mu} {\mkern 1mu} kJ{\mkern 1mu} {\mkern 1mu} mo{l^{ - 1}},{\mkern 1mu} {\mkern 1mu} $
${\Delta _{hyd}}H_{C{l^ - }}^\Theta {\mkern 1mu} = {\mkern 1mu} {\mkern 1mu} - {\mkern 1mu} 381{\mkern 1mu} kJ{\mkern 1mu} {\mkern 1mu} mo{l^{ - 1}})$