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hw13solutions

# hw13solutions - Niu(qn269 HW13 Tsoi(58020 This print-out...

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Niu (qn269) – HW13 – Tsoi – (58020) 1 This print-out should have 20 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Given: specific heat capacity = 4180 J / kg · C and latent heat of vaporization of water = 2 . 26 × 10 6 J / kg . You have 92 g of steam at 100 C. How much heat must be removed to change it to 92 g of water at 15 C? Correct answer: 2 . 40608 × 10 5 J. Explanation: Given : m = 92 g = 0 . 092 kg , c = 4180 J / kg · C , L v = 2 . 26 × 10 6 J / kg , T o = 100 C , and T f = 15 C . First, the steam must be condensed into water( Q = m L v ), then the water must be cooled( Q = m c Δ T ). Thus the heat loss is Q = m L v + m c Δ T = m L v + m c ( T o - T f ) = (0 . 092 kg) (2 . 26 × 10 6 J / kg) + (0 . 092 kg) (4180 J / kg · C) × (100 C - 15 C) = 2 . 40608 × 10 5 J . 002 10.0 points Given: specific heat of water = 1 cal / g · C and latent heat of ice = 79 . 7 cal / g One liter of water at 42 C is used to make iced tea. How much ice at 0 C must be added to lower the temperature of the tea to 20 C? Correct answer: 220 . 662 g. Explanation: Given : m w = 1 L = 1000 g , c w = 1 cal / g · C , T h = 42 C , T c = 20 C , T 0 = 0 C , and L ice = 79 . 7 cal / g . Q melt ice + Q raise to 10 C = Q lost by water m ice L ice + m ice c water Δ T ice = m water c water Δ T water m ice = m water c w Δ T w L ice + c w Δ T ice Since L ice + c w Δ T ice = (79 . 7 cal / g) + (1 cal / g · C) (20 C - 0 C) = 99 . 7 cal / g then m ice = m water c w ( T h - T c ) L ice + c w ( T c - T 0 ) = (1000 g) (1 cal / g · C) (42 C - 20 C) 99 . 7 cal / g = 220 . 662 g . 003 10.0 points When water freezes 1. the temperature of the water decreases. 2. there is no heat exchange with the sur- roundings. 3. heat is absorbed from the surroundings. 4. the temperature of the water increases. 5. heat is given off to the surroundings. cor- rect Explanation: While water freezes, it gives away heat to the surroundings but its temperature remains the same; in addition, its volume increases. 004 (part 1 of 2) 10.0 points

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Niu (qn269) – HW13 – Tsoi – (58020) 2 A 1 . 1 kg bar of copper is heated at atmo- spheric pressure of 1 . 013 × 10 5 N / m 2 . If its temperature increases from 16 C to 48 C, find the work done by the copper. The linear expansion coefficient of copper is 1 . 7 × 10 5 ( C) 1 , and its density is 8920 kg / m 3 .
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hw13solutions - Niu(qn269 HW13 Tsoi(58020 This print-out...

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