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Ch.9 - Thermochemistry: Chemical Energy
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All textbooksMcMurry 8th EditionCh.9 - Thermochemistry: Chemical EnergyProblem 2

Chapter 9, Problem 2

A room-temperature balloon filled with air is placed in the freezer and the balloon contracts. What is the sign of q and w for the air inside the balloon? (LO 9.4) (a) q = +, w = - (b) q = +, w = + (c) q = -, w = - (d) q = -, w = +

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Hello everyone today. We have the following problem. A sample of gas is placed in a container with a movable piston. The entire apparatus is heated and the gas is allowed to expand, identify the signs for Q and W. For the gas inside the container. So as stated, we know that the gas is heated so as the gas heats up this heat energy from the heat is absorbed, and thus this is going to lead to a positive Q sign or heat sign. And so we can get rid of answer choices C and D. We also know that the gas expands so the gas is going to occupy a lot more space, and so this is indicative of a volume. The change in volume is going to increase in this directly leads to a decrease in our work or W. So our heat is going to be positive and our work is going to be negative. And so that's going to lead to answer choice B being our correct answer. And with that we have answered the question overall. I hope it has helped. And until next time.
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Textbook Question

Several processes are given in the table and labeled as endo- thermic or exothermic and given a sign for ∆H°. Which process is labeled with the correct sign of ∆H° and correct classification as endothermic or exothermic? (LO 9.8) Process (a) Ammonium nitrate dissolves in water, and the temperature of the solution decreases.

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Textbook Question

Several processes are given in the table and labeled as endo- thermic or exothermic and given a sign for ∆H°. Which process is labeled with the correct sign of ∆H° and correct classification as endothermic or exothermic? (LO 9.8) Process (b) Methane, the main component of natural gas, is burned to produce a flame on a stovetop.

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