Respuesta :
The enthalpy is the amount of heat present in a system. The enthalpy change of a reaction is given by the difference between the enthalpy of formation of products and reactants
The change in enthalpy for the combustion reactions are;
- a. ΔH for the combustion of 1.0 mol of isooctane is 5,100.07 kJ
- b. ΔH for the combustion of one gallon of isooctane is 116,083.183 kJ
The reason the above values are correct are as follows:
ΔHrxn = The sum of enthalpies of formation of the products - The sum of enthalpies of formation of the reactants
a. The combustion of isooctane is presented as follows;
2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O
The thermodynamic data required (obtained from a similar question) are;
H₂(g) + (1/2)O₂(g) → H₂O(g) ΔH⁰ = -241.8 kJ
C(s) + O₂(g) → CO₂(g) ΔH⁰ = -393.5 kJ
8C(s) + 9H₂(g) → C₂H₁₈(l) ΔH⁰ = -224.13 kJ
Therefore, we get;
(-224.13 kJ) + ΔH = 8 × (-393.5 kJ) + 9 × (-241.8 kJ)
ΔH rxn = 5,100.07 kJ
- The change in enthalpy for the combustion of 1.0 mol of isooctane is 5,100.07 kJ
b. The mass one gallon of isooctane, m = 2.6 kg - 2,600 g
The molar mass of isooctane = 114.23 g/mol
The number of moles of isooctane in 2,600 g of isooctane is given as follows
n = 2,600 g/(114.23 g/mol) ≈ 22.76 moles
The enthalpy change for the combustion of one gallon of isooctane is therefore;
ΔH = n × ΔH rxn = 22.76 moles × 5,100.07 kJ/mol ≈ 116,083.183 kJ
- The enthalpy change for the combustion of one gallon of isooctane ≈ 116,083.183 kJ
Learn more about the enthalpy in chemical reactions here:
https://brainly.com/question/12902391
