Courtesy of Reg :)
5.18(a) Write an equation that expresses the first law of thermodynamics. (b) In applying the first law, do we need to measure the internal energy of a system? Explain. (c) Under what conditions will the quantities q and w be negative numbers?
5.19 Calculate (delta)E, and determine whether the process is endothermic or exothermic for the following cases: (a) A system releases 113kJ of heat to the surroundings and does 39kJ of work on the surroundings. (b) q=1.62kJ and w=-874J; (c) The system absorbs 77.5kJ of heat while doing 63.5 kJ of work on the surroundings.
5.20 For the following processes, calculate the change in internal energy of the system, and determine whether the process is endothermic or exothermic: (a) A balloon is heated by adding 900J of heat. It expands, doing 422J of work on the atmosphere. (b) a 50-g sample of water is cooled from 30 degrees C to 15 degrees C, thereby losing approximately 3140J of heat. (c) A chemical reaction releases 8.65kJ of heat and does no work on the surroundings.
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