chem hw3

chem hw3 - rose(kmr2427 – Homework 3 – fakhreddine...

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Unformatted text preview: rose (kmr2427) – Homework 3 – fakhreddine – (51615) 1 This print-out should have 9 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 1.0 points Mixing 17.6 kg of ethylene glycol (commercial antifreeze, C 2 H 6 O 2 ) with 6.00 gal of water lowers the freezing point to- 10 . ◦ F. Suppose you wanted to accomplish the same thing with sugar (sucrose, C 12 H 22 O 11 ) instead of ethy- lene glycol. How many kilograms of sucrose would you use? 1 gallon = 3.785 liters. K f for water = 1 . 86 ◦ C/m. 1. 3.09 kg 2. 6019 kg 3. 4 . 68 × 10 − 3 kg 4. 97.1 kg correct 5. 17.6 kg Explanation: 002 1.0 points 10 grams of NaNO 3 is dissolved in 750 grams of water. What is the boiling point elevation in degrees Celsius? Note that K b for water is 0.512 ◦ C /m . Assume complete dissociation of the salt and ideal behavior of the solution. Correct answer: 0 . 160627 ◦ C. Explanation: m NaNO 3 = 10 g m water = 750 g K b water = 0 . 512 ◦ C /m NaNO 3 → Na + + NO − 3 i = 2 m = (10 g NaNO 3 ) parenleftBig 1 mol NaNO 3 85 . 0 g NaOH parenrightBig = 0 . 117647 mol NaNO 3 Δ T b = K b · m · i = parenleftbigg . 512 ◦ C m parenrightbiggparenleftbigg . 117647 . 75 m parenrightbigg (2) = 0 . 160627 ◦ C 003 1.0 points Each of the following samples was placed in 1 liter of water. I) 0.6 mol NaOH II) 0.7 mol KCl III) 0.5 mol Na 2 NO 3 IV) 1 mol of sugar Rank the solutions that are made in terms of increasing order of boiling point elevation. (Remember your solubility rules.) 1. II, IV, I, III 2. III, I, II, IV 3. III, I, IV, II 4. IV, II, I, III 5. IV, I, II, III correct Explanation: Colligative properties of a solution depend on the number of solute particles in solution, not the type....
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chem hw3 - rose(kmr2427 – Homework 3 – fakhreddine...

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