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Unformatted text preview: PHYS-408 Fall 2008 Mastering Physics Assignment #3 Solutions Problem 16.8 An element in its solid phase has mass density 1750 (kg)/m 3 and number density 4.39 * 10 28 (atoms)/ m 3 . (a) What is the element's atomic mass number? If we have one meter cubed of the element, then there would be 4.39 10 28 atoms. The number of moles would then be n = 4.39 10 28 N A = 4.39 10 28 6.02 10 23 / mol = 72924 mol This would mass 1750 kg , so the mass of one mole would be 1750 kg 72924 mol = 0.024 kg = 24 g so A = 24 . Problem 16.18 A gas at 100 degree(s) C fills volume V . (a) If the pressure is held constant, what is the volume if the Celsius temperature is doubled? This is a simple application of the ideal gas law. pV = nRT V T = nR p = constant so V T = V 1 T 1 Of course, the temperatures have to be in Kelvins, so T = 100 o C = 373 K T 1 = 200 o C = 473 K so V 1 V = T 1 T = 473 K 373 K = 1.27 (b) If the pressure is held constant, what is the volume if the Kelvin temperature is doubled?doubled?...
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