Extra Credit Homework 23 Solutions

Extra Credit Homework 23 Solutions - lim(kl9356 Extra...

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lim (kl9356) – Extra Credit Homework 23 – Weathers – (17104) 1 This print-out should have 15 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 (part 1 oF 2) 10.0 points Given: R = 8 . 31451 J / K · mol . How much work is done by the steam when 1 . 1 mol oF water at 100 C boils and becomes 1 . 1 mol oF steam at 100 C at 1 . 3 atm pres- sure? Correct answer: 3411 . 18 J. Explanation: Given : n = 1 . 1 mol , R = 8 . 31451 J / K · mol , T = 100 C = 373 K , m = 18 g / mol , P = 1 . 3 atm and ρ = 1 g / cm 3 . Using the ideal gas law, P V = nRT . m is the molar mass oF water. The work done is W = P Δ V = nRT n p mP ρ P = (1 . 1 mol) (8 . 31451 J / K · mol) (373 K) (1 . 1 mol) (18 g / mol) (1 . 3 atm) 1 g / cm 3 × ± m 100 cm ² 3 1 . 013 × 10 5 Pa 1 atm = 3411 . 18 J . 002 (part 2 oF 2) 10.0 points ±ind the change in internal energy oF the steam as it vaporizes. Consider the steam to be an ideal gas with heat oF vaporization 2 . 26 × 10 6 J / kg. Correct answer: 41 . 3368 kJ. Explanation: Given : L v = 2 . 26 × 10 6 J / kg The heat needed to vaporize the water is Q = nmL v ±rom the frst law oF thermodynamics Δ U = Q W = v W = b (1 . 1 mol) (18 g / mol) 1 kg 1000 g × (2 . 26 × 10 6 J / kg) 3411 . 18 J B 1 kJ 1000 J = 41 . 3368 kJ . 003 10.0 points One mole oF an ideal gas is heated at constant pressure so that its temperature increases by a Factor oF 8. Then the gas is heated at constant temperature so that its volume increases by a Factor oF 8. ±ind the ratio oF the work done during the isothermal process to that done during the isobaric process. Correct answer: 2 . 3765. Explanation: Given : k = 8 . The work done in the isobaric process is W ab = i b a P dV = P a ( V b V a ) = nR ( k T a ) a = ( k 1) a , The work done in the isothermal process is W bc = i c b P dV = b i c b dV V = b ln p V c V b P = ( k T a ) ln k , ThereFore the ratio Fraction is r = W bc W ab = ( k T a ) ln k ( k 1) a = k ln k k 1 = 8 ln(8) (8 1) = 2 . 3765 .
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lim (kl9356) – Extra Credit Homework 23 – Weathers – (17104) 2 004 10.0 points The surface of the Sun has a temperature of about 5741 K.
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Extra Credit Homework 23 Solutions - lim(kl9356 Extra...

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