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# Homework 2 Sutcliffe Answers - huynh(hph268 Homework 2...

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huynh (hph268) – 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 4 . 6 g of iodine at 144 C? Correct answer: 0 . 302679 kJ. Explanation: 002 10.0 points 3790 J of heat are added to a 20 . 9 g sample of iron at 30 C. What is the final tempera- ture of the iron? The specific heat of iron is 0 . 449 J / g · K. Correct answer: 706 . 875 K. Explanation: q = 3790 J T i = 30 C + 273 = 303 K m = 20 . 9 g T f = ? SH iron = 0 . 449 J / g · K SH iron = q m Δ T Δ T = q m SH iron = 3790 J (20 . 9 g)(0 . 449 J / g · K) = 403 . 875 K Δ T = T f - T i T f = Δ T + T i = 403 . 875 K + 303 K = 706 . 875 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 50 g of steam at 116 C are completely converted to ice at - 12 . 4 C. Correct answer: 153 . 52 kJ. Explanation: Cool the steam to 100 C: q 1 = (50 g) parenleftbigg 2 . 03 J g · C parenrightbigg (116 C - 100 C) = 1624 J Condense the steam to water: q 2 = (50 g) (2260 J / g) = 1 . 13 × 10 5 J Cool the water to 0 C: q 3 = (50 g) parenleftbigg 4 . 18 J g · C parenrightbigg (100 C) = 20900 J Freeze the water: q 4 = (50 g) (334 J / g) = 16700 J Cool the ice to - 12 . 4 C: q 5 = (50 g) parenleftbigg 2 . 09 J g · C parenrightbigg [0 C - ( - 12 . 4 C)] = 1295 . 8 J The total heat is q = 1 . 5352 × 10 5 J = 153 . 52 kJ . 004 10.0 points 74 g sodium nitrate is dissolved in water to make 820 g of solution. What is the percent sodium nitrate in the solution? 1. 9 . 91957% 2. 9 . 02439% correct

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huynh (hph268) – Homework 2 – Sutcliffe – (51060) 2 3. 0 . 0902439% 4. 100% Explanation: m NaNO 3 = 74 g m soln = 820 g percent = mass solute mass solution × 100 % = 74 g NaNO 3 820 g solution × 100 % = 9 . 02439% 005 (part 1 of 2) 10.0 points A student investigating the properties of so- lutions containing carbonate ions prepared a solution containing 5 .
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