Answer :
Answer: B) -4819 kJ
Explanation:
The balanced reaction for combustion of octane is:
[tex]2C_8H_{18}+25O_2\rightarrow 16CO_2+18H_2O[/tex] [tex]\Delta H^0_{rxn}=-11018kJ[/tex]
To calculate the number of moles, we use the equation:
[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}[/tex]
given mass of octane = 100.0 g
Molar mass of octane = 114.33 g/mol
Putting in the values we get:
[tex]\text{Number of moles}=\frac{100.0g}{114.33g/mol}=0.8747moles[/tex]
According to stoichiometry:
2 moles of octane give heat = -11018 kJ
Thus 0.8747 moles of octane give =[tex]\frac{-11018}{2}\times 0.8747=-4819kJ[/tex]
Thus -4819 kJ of heat is released by 100.0 g of octane assuming complete combustion.
The heat associated with the combustion of 100.0 g of octane, assuming complete combustion, is B) -4819 kJ.
Let's consider the following thermochemical equation.
2 C₈H₁₈ + 25 O₂ → 16 CO₂ + 18 H₂O ΔH°rxn = -11018 kJ
First, we will convert 100.0 g of octane to moles using its molar mass (114.33 g/mol).
[tex]100.0 g \times \frac{1mol}{114.33g} = 0.8747mol[/tex]
According to the thermochemical equation, 11018 kJ of heat are evolved when 2 moles of octane are combusted. The heat associated with the combustion of 0.8747 moles of octane is:
[tex]0.8747 mol \times \frac{(-11018kJ)}{2mol} = -4819 kJ[/tex]
The heat associated with the combustion of 100.0 g of octane, assuming complete combustion, is B) -4819 kJ.
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