Problem Set 14 Key with Full Answers

Problem Set 14 Key with Full Answers - Problem Set 14 h...

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h higher melting point and boiling point than C 3 H 8 , propane, which only has intermolecular dispersion forces. Problem Set 14 Dr. Sparks, Fall 2010 Heating Curves 1. Calculate the amount of heat needed for each process. Answer in joules. a. to raise the temperature of 150g of water from 15°C to 35°C. Since we are still below the boiling point of water, we use the specific heat for H 2 O(l) = = . ° ° - ° = . = . . q nC∆T 150 g4 18J C∙g35 C 15 C 15083 6 J 1 58 36x103 12600 J This is very close to the actual value of 12,540 J b. to heat 150 g water from 30°C to 90°C = = . ° ° = . q nC∆T 150 g4 18J C∙g60 C 9x1034 18J 37000 J This is close to the actual value of 37,620 J c. to cool 2 moles water from 75°C to 25°C? = = * / . ° - ° = . - ≈- . . . q nC∆T 2 mol 18g mol4 18J C∙g25 75 C 364 18 50 J 3 64 25 0 ≈- . ≈- ≈- x102 J 3 621 x102 J 75x102 7500 J This is close to the actual value of -7524 J. 2. Draw a chart with the heating curve for a substance with the following melting points and boiling points: MP = 15°C, BP = 110°C a. What state is substance in at 10°C? A. solid B. liquid C. gas D. solid and/or liquid E. liquid and/or gas b. What state is substance in at 110°C? A. solid B. liquid C. gas D. solid and/or liquid E. liquid and/or gas 3. Draw a chart of C3H8. Now draw one with the same heat and temperature scales for NH3.
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4. How much energy is released when 200 g liquid water at 40°C freezes and forms ice with a temperature of -50°C? Would q have a positive or negative value? The water is a liquid at 40°C, so first it needs to cool to 0°C and then freeze and then the
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This note was uploaded on 06/23/2011 for the course CH 301 taught by Professor Fakhreddine/lyon during the Fall '07 term at University of Texas at Austin.

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Problem Set 14 Key with Full Answers - Problem Set 14 h...

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