The combustion of octane can be represented by the equation
$$2C_8H_{18}(g) + 25O_2(g) \rightarrow 16CO_2(g) + 18H_2O(g) \quad \Delta H = -10\, 108 \text{ kJ mol}^{-1}$$
The energy produced, in kJ, by the complete oxidation of 45 kg of octane is
A - VCE - SSCE Chemistry - Question 4 - 2003 - Paper 1
Question 4
The combustion of octane can be represented by the equation
$$2C_8H_{18}(g) + 25O_2(g) \rightarrow 16CO_2(g) + 18H_2O(g) \quad \Delta H = -10\, 108 \text{ kJ mol}^{... show full transcript
Worked Solution & Example Answer:The combustion of octane can be represented by the equation
$$2C_8H_{18}(g) + 25O_2(g) \rightarrow 16CO_2(g) + 18H_2O(g) \quad \Delta H = -10\, 108 \text{ kJ mol}^{-1}$$
The energy produced, in kJ, by the complete oxidation of 45 kg of octane is
A - VCE - SSCE Chemistry - Question 4 - 2003 - Paper 1
Step 1
Calculate the number of moles of octane in 45 kg
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Answer
The molar mass of octane (C₈H₁₈) is approximately 114 g/mol. To convert 45 kg to grams:
45extkg=45,000extg
Now, calculate the number of moles:
Number of moles=114extg/mol45,000extg≈394.74extmol
Step 2
Calculate the total energy produced
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Answer
From the combustion reaction, the energy produced by the complete combustion of 1 mole of octane is -10,108 kJ.
Thus, the total energy produced by 394.74 moles is:
Total energy=Number of moles×ΔH
Substituting values:
Total energy=394.74 mol×(−10,108 kJ/mol)≈−3.99×106 kJ
Step 3
Determine the magnitude of the energy produced
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Answer
The energy produced in absolute terms is approximately 3.99 × 10⁶ kJ. Since the options are given in scientific notation, this rounds to:
