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# chem5 - Homework 5 1 When gasoline burns in a car engine...

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Homework 5 1) When gasoline burns in a car engine, the heat released causes the reaction products CO 2 and H 2 O to expand pushing the pistons outward. Excess heat is removed by the car's cooling system. If the expanding gases do 475 J of work on the pistons and the system loses 328 J to the surroundings as heat, calculate the change in energy (ΔE) in both kJ and kcal. 2) A 25.0 g sample of Iridium, Ir, is heated by exposure to 1.50 x 10 3 J. The temperature of the Ir is raised by 458 o C. What is the specific heat of Ir in J/g· o C? 3) Given this reaction and information: 2 N 2(g) + 3 O 2(g) 2 NO 2(g) + 2 NO (g) ΔH = +247 kJ/mol suppose that 33.6 g of N 2 reacts with 49.7 g of O 2 . Answer the following questions about this reaction. How many moles of reaction have occurred in this particular situation? What is the total amount of heat released/absorbed by this reaction when 33.6 g of N 2 reacts with 49.7 g of O 2 ? (Do NOT enter the + or - sign.) 4) Calculate the kinetic energy, in joules, of a 78 g golf ball moving at 51 m/s. Convert your answer from the first part of the question to calories.

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