<u>Answer:</u> The enthalpy of the reaction is 269.4 kJ/mol
<u>Explanation:</u>
To calculate the heat absorbed by the calorimeter, we use the equation:

where,
q = heat absorbed
c = heat capacity of calorimeter = 675 J/°C
= change in temperature = 
Putting values in above equation, we get:

To calculate the heat absorbed by water, we use the equation:

where,
q = heat absorbed
m = mass of water = 925 g
c = heat capacity of water = 4.186 J/g°C
= change in temperature = 
Putting values in above equation, we get:

Total heat absorbed = 
Total heat absorbed = ![[19993.5+114690.12]J=134683.62J=134.7kJ](https://tex.z-dn.net/?f=%5B19993.5%2B114690.12%5DJ%3D134683.62J%3D134.7kJ)
To calculate the enthalpy change of the reaction, we use the equation:

where,
q = amount of heat absorbed = 134.7 kJ
n = number of moles of hydrocarbon = 0.500 moles
= enthalpy change of the reaction
Putting values in above equation, we get:

Hence, the enthalpy of the reaction is 269.4 kJ/mol