Chapter 6 - Thermodynamics_Part3

# Chapter 6 - Thermodynamics_Part3 - GENERAL CHEMISTRY...

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GENERAL CHEMISTRY CHAPTER 6 – THERMODYNAMICS PAGE 9 OF 16 Example : Calculate E given that q = +82 kJ and w = - 47 kJ. Explain what is happening from the system’s point of view. How to Measure E by Experiment Since E = q + w, we can determine E by measuring q and w In practice, it is easiest to do a process in such a way that there is no change in volume w = 0 w = -P V ; but w = 0 at constant volume At constant volume E reaction = q V In practice, it is not possible to observe the temperature changes of the individual chemicals involved in a reaction Instead, we use an insulated, controlled surroundings and measure the temperature change in it The surroundings is called a bomb calorimeter and is usually made of a sealed, insulated container filled with water Designed to measure E for combustion reactions The temperature change ( T) is related to the heat absorbed by the entire calorimeter (q Cal ): q Cal = C cal x T C cal = heat capacity of the entire calorimeter assembly (determined by measurement) Assuming no heat escapes from the calorimeter: The amount of heat gained by the calorimeter = the heat released by the reaction q calorimeter = - q reaction at constant volume q surroundings = - q system - E reaction = q cal = C cal x T

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## Chapter 6 - Thermodynamics_Part3 - GENERAL CHEMISTRY...

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