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Nitrogen is an ideal gas with Cv=20.8Jmol1K1. (a) Three moles of nitrogen at 30C, contained in a rigid vessel, is heated to 250C. How much heat is required if the vessel has negligible heat capacity? If the vessel weighs 100kg and has a heat capacity of 0.5kJ1 K1, how much heat is required? (b) Four moles of nitrogen at 200C is contained in a piston-cylinder arrangement. How much heat must be extracted from this system, which is kept at constant pressure, to cool it down to 40C if the heat capacity of the piston and cylinder is neglected? [30 marks]