Horatio Meshuggeneh has his own ideas of how to do things.

Horatio Meshuggeneh has his own ideas of how to do things. For instance, when given the task of determining an oven temperature, most people would use a thermometer. Being allergic to doing anything most people would do, however, Meshuggeneh instead performs the following experiment. He puts a copper bar with a mass of 5.0 kg in the oven and puts ΔH? = 2919 an identical bar in a well-insulated 20.0-liter vessel containing 5.00 L of liquid water and the remainder saturated steam at 760 mm Hg absolute. He waits long enough for both bars to reach thermal equilibrium with their surroundings, then quickly takes the first bar out of the oven, removes the second bar from the vessel, drops the first bar in its place, covers the vessel tightly, waits for the contents to come to equilibrium, and notes the reading on a pressure gauge built into the vessel. The value he reads is 50.1mm Hg. He then uses the facts that copper has a specific gravity of 8.92 and a specific internal energy given by the expression U (kJ/kg) = 0.36T(°C) to calculate the oven temperature.

(a) The Meshuggeneh assumption is that the bar can be transferred from the oven to the vessel with, out any heat being lost. If he makes this assumption, what oven temperature does Meshuggeneh calculate? How many grams of water evaporate in the process? (Neglect the heat transferred to the vessel wall—i.e., assumes that the heat lost by the bar is transferred entirely to the water in the vessel. Also, remember that you are dealing with a closed system once the hot bar goes into the vessel.)

(b) In fact, the bar lost 8.3 Id of heat between the oven and the vessel. What is the true oven temperature?

(c) The experiment just described was actually Meshuggeneh second attempt. The first time he tried it, the final gauge pressure in the vessel was negative. What had he forgotten to do?

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