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AP Chemistry
6.4 Heat Capacity and Calorimetry
AdvancedMCQExperimental16.9k
A line drawing in grayscale shows a cross-section of a bomb calorimeter apparatus. An outer insulated container with double walls holds a bath of liquid water. Submerged in the water is a cylindrical sealed steel reaction vessel resting on a small base. Extending vertically from the top cover into the water bath are two components: a motorized stirrer with two propeller blades on the left, and a digital temperature probe on the right. Two thin ignition wires pass through the top cover directly into the top of the steel reaction vessel. Labels appear exactly once: Thermometer, Stirrer, Insulated jacket, Water, Reaction chamber, and Ignition leads. No other apparatus, labels, text, or annotations appear.
Schematic diagram of the constant-volume calorimeter apparatus.
A student uses the constant-volume calorimeter shown to determine the standard molar enthalpy of combustion, \(\Delta H_{\text{comb}}^\circ\), of a solid fuel. A \(0.0100\text{ mol}\) sample of the fuel is placed in the reaction chamber and completely combusted in excess oxygen. The student records the temperature increase, \(\Delta T\), of the \(1000\text{ g}\) of surrounding water. In the calculations, the student assumes all heat released by the combustion is absorbed solely by the water (\(q_{\text{absorbed}} = m_{\text{water}} c_{\text{water}} \Delta T\)) and neglects the heat capacity of the calorimeter vessel and internal components, \(C_{\text{cal}}\).

Which of the following correctly predicts the effect of this assumption on the calculated \(\Delta H_{\text{comb}}^\circ\) and identifies the appropriate experimental procedure to determine \(C_{\text{cal}}\)?

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