solution_hw 2 sut - silva (jrs4378) Homework 2 Sutcliffe...

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Unformatted text preview: silva (jrs4378) Homework 2 Sutcliffe (51060) 1 This print-out should have 16 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. Read the questions carefully. Look for whether youve been give or asked for mo- LaRity or moLaLity! There will be one more HW that will include the rest of Chapter17. 001 10.0 points NOTE: elemental iodine means the ques- tion wants you to remember the standard state of iodine. The molar heat of fusion of elemental iodine is 16.7 kJ/mol at its normal melting point of 144 C. What quantity of heat is required to melt 1 . 6 g of iodine at 144 C? Correct answer: 0 . 10528 kJ. Explanation: 002 10.0 points 3620 J of heat are added to a 28 . 1 g sample of iron at 23 C. What is the final tempera- ture of the iron? The specific heat of iron is . 449 J / g K. Correct answer: 582 . 917 K. Explanation: q = 3620 J T i = 23 C + 273 = 296 K m = 28 . 1 g T f = ? SH iron = 0 . 449 J / g K SH iron = q m T T = q m SH iron = 3620 J (28 . 1 g)(0 . 449 J / g K) = 286 . 917 K T = T f- T i T f = T + T i = 286 . 917 K + 296 K = 582 . 917 K 003 10.0 points Consider the specific heats C H 2 O (s) = 2 . 09 J g C . C H 2 O ( ) = 4 . 18 J g C . C H 2 O (g) = 2 . 03 J g C . The heat of fusion for water is 334 J/g and the heat of vaporization for water is 2260 J/g. Calculate the amount of heat absorbed when 27 g of steam at 123 C are completely converted to ice at- 21 . 8 C. Correct answer: 83 . 8148 kJ. Explanation: Cool the steam to 100 C: q 1 = (27 g) parenleftbigg 2 . 03 J g C parenrightbigg (123 C- 100 C) = 1260 . 63 J Condense the steam to water: q 2 = (27 g) (2260 J / g) = 61020 J Cool the water to 0 C: q 3 = (27 g) parenleftbigg 4 . 18 J g C parenrightbigg (100 C) = 11286 J Freeze the water: q 4 = (27 g) (334 J / g) = 9018 J Cool the ice to- 21 . 8 C: q 5 = (27 g) parenleftbigg 2 . 09 J g C parenrightbigg [0 C- (- 21 . 8 C)] = 1230 . 17 J The total heat is q = 83814 . 8 J = 83 . 8148 kJ . 004 10.0 points 71 . 8 g sodium nitrate is dissolved in water to make 865 g of solution....
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This note was uploaded on 10/23/2010 for the course CH 51060 taught by Professor Sutcliffe during the Fall '10 term at University of Texas at Austin.

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solution_hw 2 sut - silva (jrs4378) Homework 2 Sutcliffe...

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