Problem: When a 3.80-g sample of liquid octane (C8H18) is burned in a bomb calorimeter, the temperature of the calorimeter rises by 27.1 °C. The heat capacity of the calorimeter, measured in a separate experiment, is 6.21 kJ/°C. Determine ΔE for octane combustion in units of kJ/mol octane.

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FREE Expert Solution

Step 1

$$\begin{gathered} \mathbf{Q}\mathbf{ }\mathbf{=}\mathbf{ }{\mathbf{C}}_{\mathbf{cal}}\mathbf{∆}\mathbf{T} \\ \mathbf{Q}\mathbf{ }\mathbf{=}\mathbf{ }\mathbf{(}\mathbf{6}\mathbf{.}\mathbf{21}\mathbf{ }\frac{\mathbf{kJ}}{\cancel{\mathbf{°}\mathbf{C}}}\mathbf{)}\mathbf{(}\mathbf{27}\mathbf{.}\mathbf{1}\cancel{\mathbf{°}\mathbf{C}}\mathbf{)} \end{gathered}$$

Q = 168.291 kJ

Step 2

$\mathbf{3}\mathbf{.}\mathbf{80}\mathbf{ }\cancel{\mathbf{g}\mathbf{ }{\mathbf{C}}_{\mathbf{8}}{\mathbf{H}}_{\mathbf{8}}}\mathbf{ }\mathbf{\times }\frac{\mathbf{1}\mathbf{ }\mathbf{mol}\mathbf{ }{\mathbf{C}}_{\mathbf{8}}{\mathbf{H}}_{\mathbf{8}}}{\mathbf{104}\mathbf{.}\mathbf{144}\mathbf{ }\cancel{\mathbf{g}\mathbf{ }{\mathbf{C}}_{\mathbf{8}}{\mathbf{H}}_{\mathbf{8}}}}$ = 0.0365 mol C₈H₈