The internal energy : 1310.43 kJ/mol
Internal energy (ΔE) can be formulated for Calorimeter :
[tex]\tt \Delta E=C\times.\Delta t[/tex]
C= the heat capacity of the calorimeter
Δt=36.2-25.68=10.52°C
[tex]\tt \Delta E=5.73 kJ/^oC\times 10.52^oC=60.2796~kJ[/tex]
[tex]\tt \dfrac{2.67}{58,12 }=0.046[/tex]
[tex]\tt \dfrac{60.2796}{0.046}=1310.43~kJ/mol[/tex]