When a 3.80 g sample of liquid octane (c8h18) is burned in a bomb calorimeter, the temperature of the calorimeter rises by 27.3 ∘c. the heat capacity of the calorimeter, measured in a separate experiment, is 6.10 kj/∘c . determine δerxn for the combustion of octane in units of kj/mol octane?

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

a

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.