
Δerxn  for  the combustion  of octate  in  kj/mol  is  4995.48  kj/mol
calculation
Step  1 :  calculate Δ T
ΔH  =  CΔT  where
 C=  specific heat capacity= 6.10 kj/°c
ΔT = change in temperature =  27.3 °c
ΔH  is  therefore =  27.3 °c  x  6.10  kj/°c  =166.53  kj
Step 2:  calculate ΔH  per  gram
ΔH  per  gram  of the sample=  166.53 kj/ 3.80 g  = 43.82  kj/g
Step: calculate ΔH  erxn  in  kj/mol
Δ H erxn  in kj /mol  =  43.82  x molar mass of C8H18The molar mass  of C8H18  is =  (12  x8)  +( 1 x18)  =  114 g/mol
Δ erxn is  therefore  = 43.82  kj/g  x 114  g/mol = 4995.48 kj/mol