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The heat of combustion of butan-1-ol is 2676 kJ mol<sup>-1</sup> - HSC - SSCE Chemistry - Question 3 - 2005 - Paper 1

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The heat of combustion of butan-1-ol is 2676 kJ mol<sup>-1</sup>. What is the value of the heat of combustion in kJ g<sup>-1</sup>? (A) 30.41 (B) 36.10 (C) 44.60 (... show full transcript

Worked Solution & Example Answer:The heat of combustion of butan-1-ol is 2676 kJ mol<sup>-1</sup> - HSC - SSCE Chemistry - Question 3 - 2005 - Paper 1

Step 1

Calculate the molar mass of butan-1-ol

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Answer

The molecular formula for butan-1-ol is C<sub>4</sub>H<sub>10</sub>O. To find the molar mass:

  • Carbon (C): 4 × 12.01 g/mol = 48.04 g/mol
  • Hydrogen (H): 10 × 1.008 g/mol = 10.08 g/mol
  • Oxygen (O): 1 × 16.00 g/mol = 16.00 g/mol

Adding these together gives:

Molar mass=48.04+10.08+16.00=74.12 g/mol\text{Molar mass} = 48.04 + 10.08 + 16.00 = 74.12 \text{ g/mol}

Step 2

Convert the heat of combustion to kJ g<sup>-1</sup>

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Answer

To find the heat of combustion in kJ g<sup>-1</sup>, use the formula:

Heat of combustion (kJ g−1)=Heat of combustion (kJ mol−1)Molar mass (g/mol)\text{Heat of combustion (kJ g}^{-1}\text{)} = \frac{\text{Heat of combustion (kJ mol}^{-1}\text{)}}{\text{Molar mass (g/mol)}}

Substituting the numbers:

Heat of combustion (kJ g−1)=2676 kJ mol−174.12 g/mol≈36.10 kJ g−1\text{Heat of combustion (kJ g}^{-1}\text{)} = \frac{2676 \text{ kJ mol}^{-1}}{74.12 \text{ g/mol}} \approx 36.10 \text{ kJ g}^{-1}

Thus, the correct answer is (B) 36.10.

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